Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices

Françoise Danielle Messu-Mandeng; Charles Felix Bilong-Bilong; Jean-François Agnèse

doi:doi:10.11648/j.ijnrem.20251002.18

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Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices

Françoise Danielle Messu-Mandeng^*

, Charles Felix Bilong-Bilong

, Jean-François Agnèse

Published in International Journal of Natural Resource Ecology and Management (Volume 10, Issue 2)

Received: 30 March 2025 Accepted: 8 April 2025 Published: 23 June 2025

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Abstract

Understanding population dynamics involves key variables like growth type and body condition, the latter indicating energy acquisition, foraging behaviour, and prey availability, factors influencing species growth, reproduction, fitness, and survival in their habitat. Therefore, using accurate fish condition indices is essential. This study examined the length-weight relationships of 1010 cyprinodontiform individuals from 12 species of non-annual nothobranchiids in southern Cameroon rainforest streams and their well-being using Fulton (Kc), allometric (Ka), and relative weight (Kn) condition factors. Species differed significantly in length (F = 56.79, df = 11, p < 0.00) and weight (F = 46.66, df = 11, p < 0.00). Findings showed allometric growth patterns (p < 0.001 and R² ranging from 0.808 to 0.965); three species exhibited positive allometric growth (b > 3) and tended to be thicker, while the other species had negative allometric growth (b < 3) and tended to be thinner. Nothobranchiid growth pattern does not follow the cube law, with mean Kc values consistently below 1.0, a range proposed to be that of this fish family and not necessarily indicating a poor fish condition. Mean Ka values indicated varying feeding intensities among species, ranging from 0.29 ± 0.01 to 7.63 ± 0.21, and influenced by b-values. Mean Kn values were always greater than 1.0 across all nothobranchiids, not differing among them and reflecting good growth conditions. The study provides first insights into the growth patterns and health of the nothobranchiids within their unique ecosystem, highlighting the advantage of using multiple condition factors to describe species' physiological and ecological well-being and offering essential perspectives for sustainable management and biodiversity conservation efforts.

Published in	International Journal of Natural Resource Ecology and Management (Volume 10, Issue 2)
DOI	10.11648/j.ijnrem.20251002.18
Page(s)	143-154
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2025. Published by Science Publishing Group

Keywords

Allometric Growth, Aphyosemion, Biodiversity Sustainable Management, Condition Factors, Length-weight Relationship, Cameroon

1. Introduction

Monitoring fish stocks through fisheries is essential for ensuring the health of water bodies for sustainable practices that protect these ecosystems for future generations. Despite attempts to retain a healthy ecosystem and preserve fish biodiversity and biomass, some fisheries continue to collapse globally

[1]

. Fisheries management considers economic, social, and ecological variables to ensure fish populations meet societal needs without overfishing

[2]

. The achievement of this goal involves biometric studies that are essential for assessing fish species and estimating their biomass

[3]

. In such studies, it is crucial to determine the growth characteristics associated with the weight and length of fish

[4]

alongside the welfare of the species, which is affected by various biotic and abiotic factors, including food availability and the fish size, age, and sexual maturity, among others

[5]

. The practice involves evaluating relationships between fish length and weight (LWRs) and examining their condition indices. LWRs help determine the weight of fish at a specific length, shed light on morphological traits and growth patterns, and facilitate further research on fish populations and stock evaluations

[6-8]

As for condition factors, they are vital instruments applied in as many fields as environmental biology and conservation. Some studies link them to biotope degradation causes such as pollution, overfishing, habitat loss, and climate change; others relate them to life history traits like reproduction, survival, parasite infection, and ecological factors affecting endangered species, aiding in understanding population dynamics

[9-11]

. The nutritional and physiological state of fish reflects its condition, which offers information about its life history and habitat

[12-15]

. These factors contribute to effective fish management and ecosystem balance

[16, 17]

. Indirect morphometric condition indices, assuming that larger fish of a particular length are healthier, are widely used, with total weight being a key indicator

[6, 18, 19]

. Among these indices are the Fulton’s coefficient of condition factor (Kc), the relative weight condition factor (Kn), and the allometric condition factor (Ka)

[6, 12, 20]

, and they are essential for fish health monitoring and fisheries management

[16, 21, 22]

. Thus, the use of accurate condition factor is important in ecological studies of fish well-being.

Body relationships are well-studied in commercial fisheries for common species but limited for many freshwater fish, particularly non-edible species in less-explored areas

[23]

, with the challenges for modelling aquatic ecosystems, where specimen counts by length class are converted into biomass estimates

[24]

. An example includes the complex non-seasonal African killifish family Nothobranchiidae, which represents 19% of marketable ornamental freshwater fish endemic to Africa

[25]

. They inhabit diverse habitats within the southern plateau and coastal plain of Cameroon, hidden in pools and streams of the Lower Guinean rainforest. This region houses over 200 valuable ornamental fish species

[26]

, crucial for research and ecological studies

[27-30]

. The Nothobranchiidae includes 37 genera and 426 species

[31]

, with only five having described length-weight relationships, including a single species of the genus Aphyosemion, i.e., Aphyosemion splendopleure (Brüning, 1929)

[32, 33]

. Knowledge of the biology of these fish, especially regarding their growth and well-being in their natural habitats, is limited because their small size, catching difficulty, and non-eating value deter research interest

[34]

. Despite the potential for killifish trade development, it remains under-regulated in Africa

[25]

, often dominated by a few traders, risking sustainable fish management and resource availability

[26]

. The degradation of forest ecosystems and unsustainable activities necessitates a deeper understanding of these species’ life histories before implementing management strategies for conservation or domestication.

Therefore, this study aimed to investigate the growth type, well-being, and fitness of non-annual nothobranchiid killifish inhabiting the backwaters, brooks, and streams of the southern rainforest of Cameroon through LWRs and morphometric condition indices estimation. The results obtained contribute to the database update for these fish species to support their management strategies and/or conservation and allow future comparisons of their population dynamics.

2. Materials and Methods

2.1. Fish Sampling and Data Collection

The sampling of Cyprinodontiforms took place in deep-forest first- to second-order springs, brooklets, and streams tributaries of the Nyong and Sanaga Rivers of the Atlantic Basin of the Cameroonian coastal plain and centre-south plateau, within an area extending from 2°43ˊ2˝N to 4°02ˊ55˝N latitude and 9°51ˊ59˝E to 11°58ˊ44˝E longitude (Figure 1).

Sampling campaigns, lasting three to six days, were conducted bimonthly from January 2012 to February 2014. Specimens were collected using a rigid rectangular iron frame with a 90 cm by 60 cm hand dip net of 3 mm mesh size (Figure 2). The specimens were euthanized with clove oil and then fixed with 10% formalin before being placed into appropriately labelled vials containing 70% alcohol. In the laboratory, fish identification was based on appropriate keys

[35-38]

. Each specimen's total length (cm) and weight (mg) were measured using an ichthyometer and electronic balance. Fishing permit number 0020/ASE/MINEPIA/DIRPEC/SDARA approved the fish collection, and the handling of fish was in respect with the Cameroon National Ethical Committee (Reg. Num. FWAIRD 0001954) following the European Union on Animal Care (CEE Council 86/609) international principle guidelines.

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Figure 1. Map of the nothobranchiids sampling sites.

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Figure 2. Sampling of the nothobranchiids in the sourthern Cameroon rainforest (Photos by Messu Mandeng).

2.2. Length-weight Relationships (LWRs)

This study only included nothobranchiid species with a minimum of 15 specimens. The LWRs were estimated using the power equation

W = a L^{b},

where W is the fish’s total weight, L is the total length, a is the rate of change of weight with length (regression intercept), and b is the weight at unit length (the regression slope or the allometric coefficient), obtained from the examination of the scatter plot diagram

[12, 39]

. The determination of the a and b coefficients resulted from the logarithmic transformation of the formula as

LogW = Loga + b LogL

[12]

. The fish’s growth pattern determination followed the statistical comparison of the obtained b-value with the hypothetical isometric value 3, and an allometric growth could be of the negative (b < 3) or positive type (b > 3)

[40]

2.3. Condition Factors

Fulton's coefficient of condition factor (Kc) was computed as an approximate value

[41]

to measure individuals in the form of hypothetical fish using the formula

Kc = 100 W / L^{3}

[20]

, where W stands for the fish’s total weight and L for its total length. To assess deviations from the form of hypothetical fish

[42]

, the allometric condition factor (Ka) was estimated using the equation:

Ka = 100 W / L^{b}

, where W is the fish's total weight, L its total length, and b the allometric coefficient of the length-weight relationship

[6]

. The habitat conditions of the species were assessed by calculating the relative weight condition factor (Kn), which is a measure of an organism's deviation from the average weight in a given sample

[40, 43]

, computed as

Kn = Wo / Wc

, where Wo is the observed total weight and Wc is the predicted total weight of each fish as

Wc = a L^{b}

. A value of Kn ≥ 1 denotes good growth conditions for the fish, while a Kn < 1 indicates poor growth conditions

[12]

2.4. Statistical Analyses

Due to the small sample sizes (< 30 individuals) during some surveys, statistical analyses were conducted by compiling data from the wet and dry seasons. Length-weight relationship and condition factor mean values were considered to be representative of the area of study regardless of the sampling locations or factors also affecting the length-weight relationships such as habitat, stomach fullness, seasonal effect, age, maturity stage, and sex

[44, 45]

. Therefore, the estimated length-weight relationships and regression coefficients are taken as mean annual values, as proposed by some authors

[46-49]

The Microsoft Office Excel and Statistica software helped conduct the analyses. The fish body condition and LWRs were statistically described as mean ± standard error and presented as graphs or tables. ANOVA was used to evaluate differences in mean lengths and condition factors across the samples, highlighting the statistical significance of the regression model with a p-value of less than 0.05. For any significant ANOVA p-value, the post hoc Tukey test allowed pinpointing which pairwise comparison of means contributed to the overall significant difference observed in the computation of the F-statistic. The data were normally distributed following an evaluation by the Shapiro-Wilks test

[50]

with an assumption of the homogeneity of variances via Levene’s test

[51]

. The evaluation of the fitting model and measure of the quality of regression predictions were given by the determination coefficient (R²), which, when close to 1, indicates a better model. The Student’s t-test at a 95% confidence interval (CI) permitted checking on the hypothetical value of isometry (b = 3) to establish the growth type of fish species and to check for any difference between the mean condition values.

3. Results

3.1. Species Collected and Morphometrics

This study considered 1010 cyprinodontiform individuals from 12 species, subdivided into six subgenera of two genera. Table 1 summarises the taxonomic affiliation of the species involved. It is a revised table mentioned previously by

[52]

and inserted here for clarity and follow-up of the analyses. Nothobranchiids were harvested in shallow streams (mean depth = 14 cm; mean width = 1 m) with slowly flowing waters (0.11 m s^-1) characterised by acidic pH (5.8), high oxygenation (dissolved O₂ = 17.68 mg l^-1), poor mineralization (conductivity = 24.79 μS cm^-1), and a mean temperature of 23.61°C. There was dense marginal vegetation and a high canopy closure above the watercourse. Stream substrate was mainly made up of litter, sand, mud, and pebbles

[52]

Table 1. Taxonomic affiliation of the nothobranchiid species from the southern Cameroonian rainforest streams related to the study of length-weight relationships and condition factors.

Genus	Sub-genus	Species
Aphyosemion	Aphyosemion Myers, 1924	Aphyosemion sp.
	Chromaphyosemion Radda, 1971	A. loennbergii (Boulenger, 1903)
		A. omega (Sonnenberg, 2007)
		A. riggenbachi (Ahl, 1924)
	Kathetys Huber, 1977	A. exiguum (Boulenger, 1911)
	Mesoaphyosemion Radda, 1977	A. amoenum Radda et Pürzl, 1976
		A. obscurum (Ahl, 1924)
		A. cameronense (Boulenger, 1903)
		A. raddai Scheel, 1975
	Raddaella Huber, 1978	A. batesii (Boulenger, 1911)
	Scheelsemion Huber, 2013	A. ahli Myers, 1933
Epiplatys		Epiplatys infrafasciatus

Table 2 summarises the length, weight, length-weight regression parameters, and growth type of each of the species collected. The results indicated that the total lengths of specimens ranged from a minimum of 16 cm for Aphyosemion loennbergii to a maximum of 88 cm for Epiplatys infrafasciatus. The smallest and largest weights measured were those of Aphyosemion exiguum (39 mg) and E. infrafasciatus (4846 mg). Species differed significantly in length (F = 56.79, df = 11, p < 0.00) and weight (F = 46.66, df = 11, p < 0.00), differences especially brought about by E. infrafasciatus and Aphyosemion batesii, which presented higher values of both parameters that, however, did not differ between these two species. There were significant differences in length (F = 17.08, df = 2, p < 0.0000) and weight (F = 10.85, df = 2, p < 0.0000) between species of the subgenus Chromaphyosemion. The most statistically significant differences were observed in the mean length and mean weight between A. loennbergii and Aphyosemion omega. Meanwhile, these parameters did not differ between the species of the subgenus Mesoaphyosemion (F = 0.639, df = 3, p = 0.6).

Table 2. Total length, total weight, length-weight parameters, and growth type of 12 nothobranchiid species encountered in the southern Cameroonian rainforest streams.

Species	n	Total length (mm)		Total weight (mg)		Length-weight parameters					Growth behavior
Species	n	Range	Mean TL ± SE	Range	Mean TW ± SE	a	b	R²	CI (b)	p regression	Growth behavior
Aphyosemion sp.	18	19‒40	31.39±1.37	80‒600	251.11±33.67	0.0214	2.6903	0.8879	2.0‒3.15	< 0.001	A-
Aphyosemion loennbergii	266	16‒48	30.98±0.37	44‒700	260.43±8.4	0.0206	2.7244	0.9125	2.58‒2.86	< 0.001	A-
Aphyosemion omega	85	17‒39	26.9±0.5	43‒657	186.9±10.54	0.0199	2.7525	0.837	2.46‒3.03	< 0.001	A-
Aphyosemion riggenbachi	18	19‒40	29.11±1.3	73‒487	218.72±29.8	0.0124	2.8692	0.8665	1.99‒3.45	< 0.001	A-
Aphyosemion exiguum	100	17‒36	24.67±0.39	39‒500	147.68±8.17	0.0053	3.1603	0.8393	2.89‒3.41	< 0.001	A+
Aphyosemion amoenum	71	21‒45	32.51±0.8	51‒711	277.82±20.45	0.0154	2.7753	0.808	2.49‒3.06	< 0.001	A-
Aphyosemion obscurum	46	22‒47	33.74±0.83	66‒804	317.7±24.17	0.0028	3.2772	0.9302	2.95‒3.58	< 0.001	A+
Aphyosemion cameronense	133	19‒47	33.6±0.56	43‒656	312.27±13.53	0.019	2.7392	0.889	2.53‒2.94	< 0.001	A-
Aphyosemion raddai	83	22‒50	33.84±0.8	87‒800	338.9±21.3	0.0139	2.8357	0.9403	2.68‒2.99	< 0.001	A-
Aphyosemion batesii	61	27‒70	47.56±1.42	92‒1826	742.9±50.38	0.0744	2.3589	0.8687	2.06‒2.62	< 0.001	A-
Aphyosemion ahli	86	17‒45	30.7±0.71	46‒713	271.1±17.4	0.0219	2.7182	0.9145	2.53‒2.91	< 0.001	A-
Epiplatys infrafasciatus	43	23‒88	44.88±1.91	99‒4846	837.67±122.74	0.0054	3.0805	0.9655	2.87‒3.23	< 0.001	A+

A- (negative allometry); A+ (positive allometry); n = sample size; CI = confidence interval of the b value.

3.2. Length-weight Relationships

As shown in Table 2, the b-value of the length-weight relationships of the species ranged from 2.3589 to 3.2772. Three species exhibited a positive allometric growth, tending to be thicker. These were Aphyosemion exiguum, Aphyosemion obscurum, and E. infrafasciatus. The other species demonstrated a negative allometric growth, suggesting that their length growth is privileged over weight input and tended to be thinner. For all the species tested, the correlation between the length and weight relationships was significant (p < 0.001), with high determination coefficient R² values varying between 0.808 and 0.9655, thereby depicting a good quality of the regression predictions for the studied species (Figure 3).

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Figure 3. Length-weight relationship regression curves of the nothobranchiids in the sourthern Cameroon rainforest. (TW: total weight; TL: total length; R²: determination coefficient).

3.3. Condition Factors

Table 3. Ranges and mean values of the Fulton’s condition factor (Kc), allometric condition factor (Ka), and relative condition factor (Kn) of 12 nothobranchiid species in the southern Cameroonian rainforest streams.

Species	Fulton Kc		Allometric Ka		Relative weight Kn
Species	Range	mean Kc ± SE	Range	mean Ka ± SE	Range	mean Kn ± SE
Aphyosemion sp.	0.50‒1.20	0.75±0.04	1.46‒2.94	2.17±0.10	0.68‒1.37	1.02±0.04
Aphyosemion loennbergii	0.45‒1.76	0.81±0.01	1.21‒4.27	2.09±0.02	0.59‒2.07	1.01±0.01
Aphyosemion omega	0.46‒1.32	0.90±0.02	1.02‒2.88	2.04±0.04	0.51‒1.44	1.02±0.02
Aphyosemion riggenbachi	0.54‒1.20	0.81±0.04	0.88‒1.76	1.26±0.06	0.71‒1.42	1.02±0.05
Aphyosemion exiguum	0.37‒1.49	0.91±0.02	0.22‒0.94	0.54±0.01	0.42‒1.78	1.02±0.02
Aphyosemion amoenum	0.21‒1.06	0.73±0.02	0.45‒2.11	1.59±0.04	0.30‒1.37	1.04±0.03
Aphyosemion obscurum	0.44‒1.08	0.75±0.02	0.18‒0.39	0.29±0.01	0.65‒1.38	1.02±0.02
Aphyosemion cameronense	0.35‒1.37	0.77±0.01	0.94‒3.03	1.90±0.03	0.50‒1.62	1.02±0.02
Aphyosemion raddai	0.47‒1.07	0.79±0.01	0.84‒1.89	1.41±0.02	0.6‒1.36	1.01±0.01
Aphyosemion batesii	0.31‒1.23	0.66±0.02	2.79‒13.12	7.63±0.21	0.38‒1.76	1.03±0.03
Aphyosemion ahli	0.44‒2.16	0.85±0.02	1.15‒5.09	2.22±0.05	0.52‒2.33	1.02±0.02
Epiplatys infrafasciatus	0.45‒1.03	0.74±0.02	0.34‒0.78	0.54±0.01	0.64‒1.42	1.01±0.02

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Figure 4. Relative condition factor (Kn), allometric condition factor (Ka), and Fulton’s condition factor (Kc) of 12 nothobranchiid species in the southern Cameroonian rainforest streams.

Table 3 presents the range and mean value estimates of the Fulton condition factor (Kc), the allometric condition factor (Ka), and the relative weight condition factor (Kn) from this study, and Figure 4 pictures the differences observed. Globally, the estimation of the well-being of the various species of this fish family using the standard condition factor tool, Fulton’s condition factor (Kc), yielded mean values less than 1, varying between 0.66 ± 0.02 for A. batesii and 0.91 ± 0.02 for A. exiguum, and differed significantly among species (F = 15.46; df = 11; p < 0.0000). A measure of the feeding rate of the species, evaluated using the allometric condition factor (Ka), showed mean values ranging from 0.29 ± 0.01 for A. obscurum to 7.63 ± 0.21 for A. batesii. Together with A. obscurum, two other species presented values of Ka < 1, namely A. exiguum and E. infrafasciatus. The Ka values also differed significantly among species (F = 866.5; df = 11; p < 0.0000). The assessment of the suitability of the habitat conditions for the fish species by the relative weight condition factor (Kn) revealed values always greater than 1 for all the species under study and not differing among them (F = 0.1117; df = 11; p = 0.999). Therefore, the habitat characteristics provide good growth conditions for these species.

4. Discussion

The purpose of this study was to use length-weight data analysis to ascertain the growth patterns of non-annual killifish in their rainforest habitat. There was a strong correlation between the body length and weight in all species. A. exiguum, A. obscurum, and E. infrafasciatus showed positive allometric growth, while other species exhibited negative allometric growth. Growth types can vary due to factors such as fish body shape (b-value)

[12, 53, 54]

, water quality, seasonal changes, fish condition, sex, gonadal development, food availability, and sampling methods

[8]	Mehanna, S. F., Farouk, A. E. Length-weight relationship of 60 fish species from the Eastern Mediterranean Sea, Egypt (GFCM-GSA 26). Frontiers in Marine Science. 2021, 8, 625422. https://doi.org/10.3389/fmars.2021.625422 View Article
[44]	Ozaydin, O., Uçkun, D., Akalin, S., Leblebici, S., Tosunoğlu, Z. Length-weight relationships of fishes captured from Izmir Bay, Central Aegean Sea. Journal of Applied Ichthyology. 2007, 23(6), 695-696. https://doi.org/10.1111/j.1439-0426.2007.00853.x View Article
[45]	Cherif, M., Zarrad, R., Gharbi, H., Missaoui, H., Jarboui, O. Length-weight relationships for 11 fish species from the Gulf of Tunis (SW Mediterranean Sea, Tunisia). Pan-American Journal of Aquatic Sciences. 2008, 3(1), 1-5.
[52]	Messu Mandeng, F. D., Bilong Bilong, C . F., Agnèse, J. F. Species diversity and distribution pattern determinants of African rivulines (Cyprinodontiformes: Nothobranchiidae) in rainforest streams of southern Cameroon. African Zoology. 2024, 59(1): 10-25. https://doi.org/10.1080/15627020.2024.2306391 View Article
[53]	Gayanilo, F. C., Pauly, D. FAO-ICLARM stock assessment tools (FiSAT): references manual. FAO Computerized information series, vol. 8; 1997, pp. 1-862.
[54]	Abowei, J. F. N. The condition factor, length-weight relationship, and abundance of Ilisha africana (Block, 1795) from Nkoro River Niger Delta, Nigeria. Advance Journal of Food Science and Technology. 2010, 2(1), 6-11.
[55]	Mommsen, T. P. Growth and metabolism. In The Physiology of Fishes. Evans, D. H. E d., CRC Press, New York; 1998, pp. 65-98.
[56]	Abujam, S. K. S., Biswas, S. P. Length-weight relationship and condition factor of spiny eel Macrognathus aral from upper Assam, India. International Journal of Current Life Sciences. 2014, 4(3), 605-611.
[57]	Abujam, S. K. S., Biswas, S. P. Length-weight relationship of spiny eel Macrognathus pancalus (Hamilton-Buchanan) from Upper Assam, India. Journal of Aquaculture Engineering and Fisheries Research. 2016, 2(2), 50-60. https://doi.org/10.3153/JAEFR16007 View Article
[58]	Ragheb, E., Akel, E. S. H. K. Some biological aspects and ﬁsheries assessment of Diplodus vulgaris (Geoffrey Saint-Hilaire, 1817) (Teleostei: Sparidae) caught by gillnets (Egyptian Mediterranean waters, Alexandria). Egyptian Journal of Aquatic Research. 2022, 48(4), 425-432. https://doi.org/10.1016/j.ejar.2022.10.001 View Article

[8, 44, 45, 52-58]

. The growth pattern of E. infrafasciatus differed from two other sympatric Epiplatys species in Nigeria's Kainji Lake Basin, where Epiplatys bifasciatus (Steindachner, 1881) showed negative allometric growth and Epiplatys spilargyreius (Duméril, 1861) displayed isometric growth

[59]

. Comparisons are hampered by the paucity of research on Aphyosemion species, although

[32]

pointed out that Aphyosemion splendopleure in Nigeria also showed negative allometric growth.

Condition indices are metrics to assess animal health and energetic status, informing on life history traits, ecology, and resource management

[9, 60, 61]

. However,

[9]

highlighted a lack of consensus on the best morphological metrics for evaluating animal well-being. Following

[39]

, the morphological condition factors Kc, Kn, and Ka were studied to understand nothobranchiid feeding behaviour and well-being in the wild. In this study, Fulton's condition factor (Kc) was less than one for all species, as observed for E. bifasciatus and E. spilargyreius in Nigeria

[59]

, suggesting that nothobranchiids may not grow according to the cube law, indicating weight gain is not proportional to length

[14]

. According to

[41]

, Kc differences among species could arise from body shape and growth type, resulting in each family having its own Kc range. We therefore propose Kc < 1 as typical for this fish family. Although not evaluated here, Kc values can vary among species or populations over time based on nutrition

[62]

. This index is widely used to investigate fish well-being because of its simplicity

[9]

, even for species with allometric growth patterns

[41]

, but assuming an isometric growth is a fair approximation for many species

[63, 64]

The species exhibited significant differences in foraging intensity, indicated by mean values of the allometric condition factor (Ka). The Ka index assesses fish feeding rates

[42, 65, 66]

; it is less used than the Fulton factor despite being more relevant for species with allometric growth or for sufficient data to minimize b-value computation errors. Both indices interpret higher values as indicative of better fish body condition

[6, 41]

. There could be physiological or genetic reasons for the observed variations in mean Ka values between species

[9]

. In this study, species with positive allometric growth (A. exiguum, A. obscurum, and E. infrafasciatus) had lower Ka than Kc values, while those with negative allometric growth had higher Ka. These results concur with those of

[41]

, who observed that Kc and Ka values were comparable for isometric growth but that Ka was higher for negative allometric growth and lower for positive allometric growth. The author suggested Ka might be more suitable for allometric growth scenarios, particularly when feeding rates and weight variations primarily influence condition factor variations.

All of the fish species under study had relative weight condition factors (Kn) greater than 1, suggesting that the stream ecosystems of tropical rainforests are favourable for their growth and survival due to the abundance of food sources

[7]

, high water quality

[52, 67]

, and low levels of predation

[68, 69]

. The presence of nothobranchiids is determined by local environmental factors like canopy cover (providing terrestrial insects falling into the streams and on which these fish mostly prey) and stream habitat characteristics kept almost constant by the vegetation cover

[52]

. Because it prevents the assumption of isometric growth and avoids a potential length effect, Kn is generally used as a proxy of individual growth if species exhibit an allometric growth pattern

[18]

. This index indicates an individual’s energy reserves (i.e., lipid and protein contents) for reproductive success and survival during food shortage

[19, 60, 70]

. By measuring variations from the average weight for length, it provides information about fish health and possible regional environmental changes

[71, 72]

. Deviations from 1 reflect variations in prey abundance and ecological factors affecting life cycles

[12, 42]

. Computing relative mass is recommended whenever possible, with attention to statistical implications

[9]

While Ka more accurately captures the effects of the environment on fish well-being simultaneously in space and time, Kc appears to be appropriate for comparing species across time or space

[41]

. When

[14]

suggests using the numerical condition factor (Kn) for assessing length-weight relationships within species,

[41]

instead found that some species can have Kc > 1 and Kn < 1, indicating good body condition despite poor growth, possibly due to life history or environmental factors that may lead species to increase their feeding intensity (described by Ka > 1). The author then suggested that Kc > 1 does not necessarily reflect better fish condition, so studying all three indices together is preferable for understanding species’ well-being. In the present study, A. batesii had the highest Ka, the lowest Kc, and a Kn similar to its congeners, indicating good feeding in favourable conditions and suggesting that relying solely on Kc can misrepresent a fish's well-being, as it assumes isometric growth, which is negatively allometric for this species. Thus, monitoring condition indices can aid in assessing fish population health or food availability and informing fisheries management

[71, 72]

5. Conclusions

The study of the growth patterns and well-being of non-annual nothobranchiid species in their natural habitat revealed that these species all displayed allometric growth types that do not follow the cube law, and differed significantly in their foraging intensities. The findings imply that tropical rainforest stream ecosystems offer favourable habitat conditions for these fish species' growth and survival and the factors contributing to their success. Results also emphasise the advantage of using multiple condition factors to describe species' physiological and ecological well-being in their habitats. Fisheries management and fish stock assessment may benefit from these findings.

Abbreviations

Ka	Allometric Condition Factor
Kc	Fulton’s Condition Factor
Kn	Relative Weight Condition Factor
LWR	Length-weight Relationship

Acknowledgments

Authors express their gratitude to the community residents who volunteered their time and helped as guides during sample collection in their localities.

Author Contributions

Françoise Danielle Messu-Mandeng: Conceptualization, Field work activities, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resource acquisition, Validation, Visualization, Writing – original draft, Writing – review & editing.

Charles Félix Bilong-Bilong: Conceptualization, Resource acquisition, Supervision, Visualization, Writing – review & editing.

Jean-François Agnèse: Conceptualization, Design, Resource acquisition, Supervision, Visualization, Writing – review & editing.

Funding

This work is not supported by any external funding.

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Tsikliras, A. C., Dinouli, A., Tsiros, V.-Z., Tsalkou, E. The Mediterranean and Black Sea ﬁsheries at risk from overexploitation. PLoS ONE. 2015, 10, e0121188.
[2]	Food and Agriculture Organization (FAO). Fisheries management. The ecosystem approach to ﬁsheries. FAO Technical Guidelines for Responsible Fisheries. Rome: Italy; 2003, No. 4, Suppl. 2.
[3]	Zargar, U. R., Yousuf, A. R., Mushtaq, B., Jan, D. Length–weight relationship of the Crucian carp, Carassius carassius in relation to water quality, sex and season in some lentic water bodies of Kashmir Himalayas. Turkish Journal of Fisheries and Aquatic Sciences. 2012, 12(3), 683-689. http://doi.org/10.4194/1303-2712-v12_3_17
[4]	Morato, T., Afonso, P., Loirinho, P., Barreiros, J. P., Sanstos, R. S., Nash, R. D. M. Length-weight relationships for 21 costal ﬁsh species of the Azores. Northeastern Atlantic. Fisheries Research. 2001, 50(3), 297-302. https://doi.org/10.1016/S0165-7836(00)00215-0
[5]	Kuriakose, S. Estimation of length weight relationship in ﬁshes. Summer school on advanced methods for fish stock assessment and fisheries management. Reprinted from the CMFRI, FRAD. Training Manual on Fish Stock Assessment and Management. 2014, pp. 1-150.
[6]	Bagenal, T. B., Tesch, F. W. Age and Growth. In Methods for Assessment of Fish Production in Freshwaters, Bagenal, T. Ed., Blackwell Scientific Publications, Oxford; 1978, pp. 101-136.
[7]	Jisr, N., Younes, G., Sukhn, C., Mohammad, H., El-Dakdouki, M. H. Length-weight relationships and relative condition factor of ﬁsh inhabiting the marine area of the Eastern Mediterranean city, Tripoli-Lebanon. Egyptian Journal of Aquatic Research. 2018, 44(4), 299-305. https://doi.org/10.1016/j.ejar.2018.11.004
[8]	Mehanna, S. F., Farouk, A. E. Length-weight relationship of 60 fish species from the Eastern Mediterranean Sea, Egypt (GFCM-GSA 26). Frontiers in Marine Science. 2021, 8, 625422. https://doi.org/10.3389/fmars.2021.625422
[9]	Stevenson, R. D., Woods, W. A. Condition indices for conservation: new uses for evolving tools. Integrative and Comparative Biology. 2006, 46(6), 1169-1190. https://doi.org/10.1093/icb/icl05
[10]	Datta, S. N., Kaur V. I., Dhawan A., Jassal, G. Estimation of length-weight relationship and condition factor of spotted snakehead Channa punctata (Bloch) under different feeding regimes. SpringerPlus. 2013, 2: 436. https://doi.org/10.1186/2193-1801-2-436
[11]	Perdana, A. W., Batubara, A. S., Nur, F. M. LWRs, condition factors and isopod parasites infection of the sumbo fish Selar crumenophthalmus (Pisces: Carangidae) in Lampulo fishing port, Banda Aceh, Aceh Province, Indonesia. IOP Conference Series: Earth and Environtal Science. 2019, 348(1): 012017. https://doi.org/10.1088/1755-1315/348/1/012017
[12]	Le Cren, E. D. The length-weight relationship and seasonal cycle in gonad weight and condition in perch (Perca fluviatilis). Journal of Animal Ecology. 1951, 20(2), 201-219. http://dx.doi.org/10.2307/1540
[13]	Schneider, J. C., Laarman, P. W., Gowing, H. Length-weight relationships. Chapter 17. In Manual of Fisheries Survey Methods II: With Periodic Updates, Michigan Department of Natural Resources, Fisheries Special Report 25, Schneider, J. C. Ed., Ann Arbor; 2000, 25(1), pp. 1-18.
[14]	Froese, R. Cube law, condition factor and weight-length relationships: history, meta-analysis and recommendations. Journal of Applied Ichthyology. 2006, 22(4), 241-253. https://doi.org/10.1111/j.1439-0426.2006.00805.x
[15]	Guidelli, G., Tavechio, W. L. G., Takemoto, R. M., Pavanelli, G. C. Relative condition factor and parasitism in anostomid ﬁshes from the ﬂoodplain of the Upper Parana River, Brazil. Veterinary Parasitology. 2011, 177(1-2), 145-151. https://doi.org/10.1016/j.vetpar.2010.11.035
[16]	Lambert, Y., Dutil, J. D. Can simple condition indices be used to monitor and quantify seasonal changes in the energy reserves of cod (Gadus morhua)? Canadian Journal of Fisheries and Aquatic Sciences. 1997, 54(S1), 104-112. https://doi.org/10.1139/f96-149
[17]	Imam, T. S., Bala, U., Balarabe, M. L., Oyeyi, T. I. Length-weight relationship and condition factor of four fish species from Wasai Reservoir in Kano, Nigeria. African Journal of General Agriculture. 2010, 6(3), 125-130.
[18]	Green, A. J. Mass/length residuals: measures of body condition or generators of spurious results. Ecology. 2001, 82(5), 1473-1483. https://doi.org/10.1890/0012-9658(2001)082[1473:MLRMOB]2.0.CO;2
[19]	Brosset, P., Fromentin, J.-M., Ménard, F., Pernet, F., Bourdeix, J.-H., Bigot, J.-L., Van Beveren, E., Pérez Roda, M. A., Choy, S., Saraux, C. Measurement and analysis of small pelagic fish condition: A suitable method for rapid evaluation in the field. Journal of Experimental Marine Biology and Ecology. 2015, 462: 90-97. https://doi.org/10.1016/j.jembe.2014.10.016
[20]	Okgerman, H. Seasonal variations in the length-weight relationship and condition factor of rudd (Scardinius erythrophthalmus L.) in Sapanca Lake. International Journal of Zoological Research. 2005, 1(1), 6-10.
[21]	Bervoets, L., Blust, R. Metal concentrations in water, sediment and gudgeon (Gobio gobio) from a pollution gradient: relationship with fish condition factor. Environmental Pollution. 2003, 126(1), 9-19. https://doi.org/10.1016/S0269-7491(03)00173-8
[22]	Cone, R. S. The need to reconsider the use of condition indices in fishery science. Transactions of the American Fisheries Society, 1989, 118(5), 510-514. https://doi.org/10.1577/1548-8659(1989)118%3C0511:TNTRTU%3E2.3.CO;2
[23]	Hossain, M. Y., Jasmine, S., Ibrahim, A. H. M., Ahmed, Z. F., Rahman, M. M., Ohtomi J. Length-weight and length-length relationships of 10 small ﬁsh species from the Ganges, Bangladesh. Journal of Applied Ichthyology. 2009, 25(1), 117-119. https://doi.org/10.1111/j.1439-0426.2008.01168.x
[24]	Kulbicki, M., Guillemot, N., Amand, M. A general approach to length–weight relationships for New Caledonian lagoon ﬁshes. Cybium. 2005, 29(3), 235-252.
[25]	Juffe-Bignoli, D., Darwall, W. R. T. Évaluation de la valeur socioéconomique des espèces d'eau douce en Afrique du Nord. Gland: World Conservation Union (IUCN); 2012, pp. 1-92.
[26]	The WorldFish Center. Africa’s age of aquarium: farming ornamental fish in the rainforests of West Africa to improve livelihoods of the poor. WorldFish Center. Penang; 2007.
[27]	Di Cicco, E., Tozzini, E. T., Rossi, G., Cellerino, A. The short-lived annual fish Nothobranchius furzeri shows a typical teleost aging process reinforced by high incidence of age-dependent neoplasias. Experimental Gerontology, 2010, 46(4), 249-256. https://doi.org/10.1016/j.exger.2010.10.011
[28]	Auer, S. K., Lopez-Sepulcre, A., Heatherly, T., Kohler, T. J., Bassar, R. D., Thomas, S. A., Reznick, D. N. Life histories have a history: effects of past and present conditions on adult somatic growth rates in wild Trinidadian guppies: Adult growth rates reflect individual history. Journal of Animal Ecology. 2012, 81(4), 818-826. https://doi.org/10.1111/j.1365-2656.2012.01964.x
[29]	Bassar, R. D., Lopez-Sepulcre, A., Reznick, D. N., Travis, J. Experimental evidence for density-dependent regulation and selection on Trinidadian guppy life histories. The American Naturalist. 2013, 181(1), 25-38. https://doi.org/10.1086/668590
[30]	Dargent, F., Torres-Dowdall, J., Scott, M. E., Ramnarine, I., Fussmann, G. F. Can mixed-species groups reduce individual parasite load? A field test with two closely related poeciliid fishes (Poecilia reticulata and Poecilia picta). Plos One. 2013, 8(2), 1-7. https://doi.org/10.1371/journal.pone.0056789
[31]	Fricke, R., Eschmeyer, W. N., Van der Laan, R. Eschmeyer's Catalog of Fishes: genera, species, references. Available from: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp (assessed 02 January 2025).
[32]	King, R. P. Length-weight relationships and related statistics of 73 populations of fish occurring in inland waters of Nigeria. Naga, ICLARM Q. 1996, 19(3), 49-52.
[33]	Froese, R., Pauly, D. FishBase. Available from: www.fishbase.org (assessed 14 January 2025).
[34]	Akpan, B. E., King, R. P., Goodluck, E. J. Diet of an African killifish Aphyosemion gardneri (Aplocheilidae) in a Nigerian rainforest pond. Acta Zoologica Sinica. 2006, 52(4), 669-675.
[35]	Amiet, J. L. Fauna of Cameroon - The genus Aphyosemion Myers (Pisces, Teleostei, Cyprinodontiformes), vol 2. Sciences Naturelles: Compiègne, France; 1987.
[36]	Sonnenberg, R. Description of three new species of the genus Chromaphysemion Radda, 1971 (Cyprinodontiformes: Nothobranchiidae) from the coastal plains of Cameroon with a preliminary review of the Chromaphyosemion splendopleure complex. Zootaxa. 2007, 1591(1), 1-38. https://doi.org/10.11646/zootaxa.1591.1.1
[37]	Van der Zee, J. R., Woeltjes, T., Wildekamp, R. H. Aplocheilidae Bleeker, 1860. In The Fresh and Brackish Water fishes of Lower Guinea, West Central Africa, Stiassny, M. L. J., Teugels, G. G., Hopkins, C. D., Ed., IRD, Paris, France; 2007, pp. 80-240.
[38]	Huber, J. H. Reappraisal of the Phylogeny of the African genus Aphyosemion (Cyprinodontiformes) focused on external characters, in line with molecular data, with new and redefined subgenera. Killi-Data Series. 2013, 2013: 4-20.
[39]	Pauly, D. Fish population dynamics in tropical waters: a manual for use with programmable calculators. International Centre for Living Aquatic Resources Management, Studies and Reviews 8, Manila; 1984.
[40]	Yilmaz, S., Yazıcıoğlu, O., Erbasaran, M., Esen, S., Zengin, M., Polat, N. Length-weight relationship and relative condition factor of white bream, Blicca bjoerkna (L., 1758), from Lake Ladik, Turkey. Journal of the Black Sea/Mediterranean Environment. 2012, 18(3), 380-387.
[41]	Ragheb, E. Length-weight relationship and well-being factors of 33 ﬁsh species caught by gillnets from the Egyptian Mediterranean waters off Alexandria. Egyptian Journal of Aquatic Research. 2023, 49(3), 361-367. https://doi.org/10.1016/j.ejar.2023.01.001
[42]	Omogoriola, H. O., Willams, A. B., Adegbile, O. M., Olakolu, F. C., Ukaonu, S. U., Myade, E. F. Length-weight relationships, condition factor (K) and relative condition factor (Kn) of Sparids, Dentex congoensis (Maul, 1954) and Dentex angolensis (Maul and Poll, 1953), in Nigerian coastal water. International Journal of Biological and Chemical Sciences. 2011, 5(2), 739-747. https://doi.org/10.4314/ijbcs.v5i2.72147
[43]	Mensah, S. A. Weight-length models and relative condition factors of nine freshwater ﬁsh species from the Yapei Stretch of the White Volta, Ghana. Elixir. Applied Zoology. 2015, 79, 30427-30431.
[44]	Ozaydin, O., Uçkun, D., Akalin, S., Leblebici, S., Tosunoğlu, Z. Length-weight relationships of fishes captured from Izmir Bay, Central Aegean Sea. Journal of Applied Ichthyology. 2007, 23(6), 695-696. https://doi.org/10.1111/j.1439-0426.2007.00853.x
[45]	Cherif, M., Zarrad, R., Gharbi, H., Missaoui, H., Jarboui, O. Length-weight relationships for 11 fish species from the Gulf of Tunis (SW Mediterranean Sea, Tunisia). Pan-American Journal of Aquatic Sciences. 2008, 3(1), 1-5.
[46]	Borges, T. C., Olim, S., Erzini, K. Weight-length relationships for fish species discarded in commercial fisheries of the Algarve (Southern Portugal). Journal of Applied Ichthyology. 2003, 19(6), 394-396. https://doi.org/10.1111/j.1439-0426.2003.00480.x
[47]	Andreu-Soler, A., Oliva-Paterna, F. J., Torralva, M. A review of length-weight relationships of fish from the Segura River basin (SE. Iberian Peninsula). Journal of Applied Ichthyology. 2006, 22(4), 295-296. https://doi.org/10.1111/j.1439-0426.2006.00719.x
[48]	Veiga, P., Machado, D., Almeida, C., Bentes, L., Monteiro, P., Oliveira, F., Ruano, M., Erzini, K., Gonçalves, J. M. S. Weight-length relationships for 54 species of the Arade Estuary, Southern Portugal. Journal of Applied Ichthyology. 2009, 25(4), 493-496. https://doi.org/10.1111/j.1439-0426.2009.01230.x
[49]	Anzueto-Calvo, M. J., Velázquez-Velazquez, E., Ruiz-Campos, G., Cruz Maza, B. G., Domínguez-Cisneros S. E. Evaluation of somatic indexes in the endangered and endemic killiﬁsh Tlaloc hildebrandi (Cyprinodontiformes: profundulidae). Neotropical Biodiversity. 2022, 8(1), 267-270. https://doi.org/10.1080/23766808.2022.2096533
[50]	Zar, J. H. Biostatistical analysis, 3^rd Ed. Prentice Hall, Upper Saddle River; 1999.
[51]	Sokal, R. R., Rohlf, F. J. Biometry: the principles and practice of statistics in biological research. Freeman, W. H. and Co. ED., New York; 1995.
[52]	Messu Mandeng, F. D., Bilong Bilong, C . F., Agnèse, J. F. Species diversity and distribution pattern determinants of African rivulines (Cyprinodontiformes: Nothobranchiidae) in rainforest streams of southern Cameroon. African Zoology. 2024, 59(1): 10-25. https://doi.org/10.1080/15627020.2024.2306391
[53]	Gayanilo, F. C., Pauly, D. FAO-ICLARM stock assessment tools (FiSAT): references manual. FAO Computerized information series, vol. 8; 1997, pp. 1-862.
[54]	Abowei, J. F. N. The condition factor, length-weight relationship, and abundance of Ilisha africana (Block, 1795) from Nkoro River Niger Delta, Nigeria. Advance Journal of Food Science and Technology. 2010, 2(1), 6-11.
[55]	Mommsen, T. P. Growth and metabolism. In The Physiology of Fishes. Evans, D. H. E d., CRC Press, New York; 1998, pp. 65-98.
[56]	Abujam, S. K. S., Biswas, S. P. Length-weight relationship and condition factor of spiny eel Macrognathus aral from upper Assam, India. International Journal of Current Life Sciences. 2014, 4(3), 605-611.
[57]	Abujam, S. K. S., Biswas, S. P. Length-weight relationship of spiny eel Macrognathus pancalus (Hamilton-Buchanan) from Upper Assam, India. Journal of Aquaculture Engineering and Fisheries Research. 2016, 2(2), 50-60. https://doi.org/10.3153/JAEFR16007
[58]	Ragheb, E., Akel, E. S. H. K. Some biological aspects and ﬁsheries assessment of Diplodus vulgaris (Geoffrey Saint-Hilaire, 1817) (Teleostei: Sparidae) caught by gillnets (Egyptian Mediterranean waters, Alexandria). Egyptian Journal of Aquatic Research. 2022, 48(4), 425-432. https://doi.org/10.1016/j.ejar.2022.10.001
[59]	Olaosebikan, B. B., Lamai, S. L., Musschoot, T. Population dynamics, life history traits of and habitat use by two sympatric nothobranchiid fishes in a tropical stream, Kainji Lake Basin, Nigeria. African Journal of Aquatic Science. 2009, 34(1) 45-56. https://doi.org/10.2989/AJAS.2009.34.1.5.730
[60]	Peig, J. Green, A. J. New perspectives for estimating body condition from mass/length data: the scaled mass index as an alternative method. Oikos. 2009, 118(12), 1883-1891. http://dx.doi. org/10.1111/j.1600-0706.2009.17643.x
[61]	Labocha, M. K., Schutz, H., Hayes, J. P. Which body condition index is best? Oikos. 2014, 123(1), 111-119. http://dx.doi.org/10.1111/j.16000706.2013.00755.x
[62]	Ricker, W. E. Computation and interpretation of biological statistics for ﬁsh populations. Bulletin of the Fisheries Research Board of Canada. 1975, 191: 1-382.
[63]	Bister, T. J., Willis, D. W., Brown, M. L., Jordan, S., Neumann, R. M., Quist, M. C., Guy, C. S. Proposed standard weight (Ws) equations and standard length categories for 18 warm water non game and riverine fish species. North American Journal of Fisheries Management. 2000, 20(2), 570-574. https://doi.org/10.1577/1548-8675(2000)020%3C0570:PSWWSE%3E2.3.CO;2
[64]	Kimmerer, W., Avent S. R., Bollens, S. M., Feyrer Grimaldo, L. F., Moyle, P. B., Nobriga, M, Visintainer, T. Variability in length-weight relationships used to estimate biomass of estuarine fish from survey data. Transactions of the American Fisheries Society. 2005, 134(2), 481-495. https://doi.org/10.1577/T04-042.1
[65]	Ighwela, K. A., Ahmed, A. B., Abol-Munaﬁ, A. B. Condition factor as an indicator of growth and feeding intensity of Nile tilapia fingerlings (Oreochromis niloticus) feed on different levels of maltose. American-Eurasian Journal of Agricultural & Environmental. 2011, 11(4), 559-563.
[66]	Faﬁoye, O., Ayodele, O. Length-Weight Relationship and Condition Factor of Four Commercial Fish Species of Oyan Lake, Nigeria. Examines in Marine Biology & Oceanography. 2018, 2(4), 227-230. https://doi.org/10.31031/EIMBO.2018.02.000543
[67]	Muchlisin, Z. A., Fransiska, V., Muhammadar, A. A., Fauzi, M., Batubara, A. S. Length-weight relationships and condition factors of the three dominant species of marine ﬁshes caught by traditional beach trawl in Ulelhee Bay, Banda Aceh City, Indonesia. Croatian Journal of Fisheries. 2017, 75(4), 104-112. https://doi.org/10.1515/cjf-2017-0014
[68]	Anderson, R. O., Newmann, R. M. Length, weight and associated structural indices. In Fisheries Techniques. Murphy, B. R., Willis, D. R. Ed., American Fisheries Society, Bethesda; 1996, pp. 447-481.
[69]	Muchlisin, Z. A., Musman, M., Siti-Azizah, M. N. Length-weight relationships and condition factors of two threatened ﬁshes, Rasbora tawarensis and Poropuntius tawarensis, endemic to Lake Laut Tawar, Aceh Province, Indonesia. Journal of Applied Ichthyology. 2010, 26(6), 949-953. https://doi.org/10.1111/j.1439-0426.2010.01524.x
[70]	Peig, J., Green, A. J. The paradigm of body condition: a critical reappraisal of current methods based on mass and length. Functional Ecology. 2010, 24(6), 1323-1332. http://dx.doi.org/10.1111/ j.1365-2435.2010.01751.x
[71]	Blackwell, B. G., Brown, M. L., Willis, D. W., Relative Weight (Wr) Status and Current Use in Fisheries Assessment and Management. Reviews in Fisheries Science. 2000, 8(1), 1-44. https://doi.org/10.1080/10641260091129161
[72]	Neumann, R. M., Guy, C. S., Willis, D. W. Length, weight, and associated indices. In Fisheries Techniques. Zale, A. V., Parrish, D. L., Sutton, T. M. Ed., American Fisheries Society, Bethesda; 2012, pp. 637-676.

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Messu-Mandeng, F. D., Bilong-Bilong, C. F., Agnèse, J. (2025). Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices. International Journal of Natural Resource Ecology and Management, 10(2), 143-154. https://doi.org/10.11648/j.ijnrem.20251002.18

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Messu-Mandeng, F. D.; Bilong-Bilong, C. F.; Agnèse, J. Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices. Int. J. Nat. Resour. Ecol. Manag. 2025, 10(2), 143-154. doi: 10.11648/j.ijnrem.20251002.18

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Messu-Mandeng FD, Bilong-Bilong CF, Agnèse J. Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices. Int J Nat Resour Ecol Manag. 2025;10(2):143-154. doi: 10.11648/j.ijnrem.20251002.18

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@article{10.11648/j.ijnrem.20251002.18,
  author = {Françoise Danielle Messu-Mandeng and Charles Felix Bilong-Bilong and Jean-François Agnèse},
  title = {Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices
},
  journal = {International Journal of Natural Resource Ecology and Management},
  volume = {10},
  number = {2},
  pages = {143-154},
  doi = {10.11648/j.ijnrem.20251002.18},
  url = {https://doi.org/10.11648/j.ijnrem.20251002.18},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijnrem.20251002.18},
  abstract = {Understanding population dynamics involves key variables like growth type and body condition, the latter indicating energy acquisition, foraging behaviour, and prey availability, factors influencing species growth, reproduction, fitness, and survival in their habitat. Therefore, using accurate fish condition indices is essential. This study examined the length-weight relationships of 1010 cyprinodontiform individuals from 12 species of non-annual nothobranchiids in southern Cameroon rainforest streams and their well-being using Fulton (Kc), allometric (Ka), and relative weight (Kn) condition factors. Species differed significantly in length (F = 56.79, df = 11, p F = 46.66, df = 11, p p R² ranging from 0.808 to 0.965); three species exhibited positive allometric growth (b > 3) and tended to be thicker, while the other species had negative allometric growth (b Kc values consistently below 1.0, a range proposed to be that of this fish family and not necessarily indicating a poor fish condition. Mean Ka values indicated varying feeding intensities among species, ranging from 0.29 ± 0.01 to 7.63 ± 0.21, and influenced by b-values. Mean Kn values were always greater than 1.0 across all nothobranchiids, not differing among them and reflecting good growth conditions. The study provides first insights into the growth patterns and health of the nothobranchiids within their unique ecosystem, highlighting the advantage of using multiple condition factors to describe species' physiological and ecological well-being and offering essential perspectives for sustainable management and biodiversity conservation efforts.},
 year = {2025}
}

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TY  - JOUR
T1  - Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices

AU  - Françoise Danielle Messu-Mandeng
AU  - Charles Felix Bilong-Bilong
AU  - Jean-François Agnèse
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N1  - https://doi.org/10.11648/j.ijnrem.20251002.18
DO  - 10.11648/j.ijnrem.20251002.18
T2  - International Journal of Natural Resource Ecology and Management
JF  - International Journal of Natural Resource Ecology and Management
JO  - International Journal of Natural Resource Ecology and Management
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EP  - 154
PB  - Science Publishing Group
SN  - 2575-3061
UR  - https://doi.org/10.11648/j.ijnrem.20251002.18
AB  - Understanding population dynamics involves key variables like growth type and body condition, the latter indicating energy acquisition, foraging behaviour, and prey availability, factors influencing species growth, reproduction, fitness, and survival in their habitat. Therefore, using accurate fish condition indices is essential. This study examined the length-weight relationships of 1010 cyprinodontiform individuals from 12 species of non-annual nothobranchiids in southern Cameroon rainforest streams and their well-being using Fulton (Kc), allometric (Ka), and relative weight (Kn) condition factors. Species differed significantly in length (F = 56.79, df = 11, p F = 46.66, df = 11, p p R² ranging from 0.808 to 0.965); three species exhibited positive allometric growth (b > 3) and tended to be thicker, while the other species had negative allometric growth (b Kc values consistently below 1.0, a range proposed to be that of this fish family and not necessarily indicating a poor fish condition. Mean Ka values indicated varying feeding intensities among species, ranging from 0.29 ± 0.01 to 7.63 ± 0.21, and influenced by b-values. Mean Kn values were always greater than 1.0 across all nothobranchiids, not differing among them and reflecting good growth conditions. The study provides first insights into the growth patterns and health of the nothobranchiids within their unique ecosystem, highlighting the advantage of using multiple condition factors to describe species' physiological and ecological well-being and offering essential perspectives for sustainable management and biodiversity conservation efforts.
VL  - 10
IS  - 2
ER  -

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Françoise Danielle Messu-Mandeng

Department of Biological Sciences, Higher Teacher’s Training College (ENS), University of Yaoundé I, Yaoundé, Cameroon

Contact Email

http://orcid.org//0000-0001-9008-8023
Charles Felix Bilong-Bilong

Department of Animal Biology and Physiology, University of Yaoundé I, Yaoundé, Cameroon

Contact Email

http://orcid.org/0000-0003-0138-5718
Jean-François Agnèse

Institute of Evolutionary Science of Montpellier (ISEM), University of Montpellier (CNRS, IRD, EPHE), Montpellier, France

Contact Email

http://orcid.org/0000-0002-6883-551X

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APA Style

Messu-Mandeng, F. D., Bilong-Bilong, C. F., Agnèse, J. (2025). Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices. International Journal of Natural Resource Ecology and Management, 10(2), 143-154. https://doi.org/10.11648/j.ijnrem.20251002.18

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ACS Style

Messu-Mandeng, F. D.; Bilong-Bilong, C. F.; Agnèse, J. Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices. Int. J. Nat. Resour. Ecol. Manag. 2025, 10(2), 143-154. doi: 10.11648/j.ijnrem.20251002.18

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AMA Style

Messu-Mandeng FD, Bilong-Bilong CF, Agnèse J. Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices. Int J Nat Resour Ecol Manag. 2025;10(2):143-154. doi: 10.11648/j.ijnrem.20251002.18

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@article{10.11648/j.ijnrem.20251002.18,
  author = {Françoise Danielle Messu-Mandeng and Charles Felix Bilong-Bilong and Jean-François Agnèse},
  title = {Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices
},
  journal = {International Journal of Natural Resource Ecology and Management},
  volume = {10},
  number = {2},
  pages = {143-154},
  doi = {10.11648/j.ijnrem.20251002.18},
  url = {https://doi.org/10.11648/j.ijnrem.20251002.18},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijnrem.20251002.18},
  abstract = {Understanding population dynamics involves key variables like growth type and body condition, the latter indicating energy acquisition, foraging behaviour, and prey availability, factors influencing species growth, reproduction, fitness, and survival in their habitat. Therefore, using accurate fish condition indices is essential. This study examined the length-weight relationships of 1010 cyprinodontiform individuals from 12 species of non-annual nothobranchiids in southern Cameroon rainforest streams and their well-being using Fulton (Kc), allometric (Ka), and relative weight (Kn) condition factors. Species differed significantly in length (F = 56.79, df = 11, p F = 46.66, df = 11, p p R² ranging from 0.808 to 0.965); three species exhibited positive allometric growth (b > 3) and tended to be thicker, while the other species had negative allometric growth (b Kc values consistently below 1.0, a range proposed to be that of this fish family and not necessarily indicating a poor fish condition. Mean Ka values indicated varying feeding intensities among species, ranging from 0.29 ± 0.01 to 7.63 ± 0.21, and influenced by b-values. Mean Kn values were always greater than 1.0 across all nothobranchiids, not differing among them and reflecting good growth conditions. The study provides first insights into the growth patterns and health of the nothobranchiids within their unique ecosystem, highlighting the advantage of using multiple condition factors to describe species' physiological and ecological well-being and offering essential perspectives for sustainable management and biodiversity conservation efforts.},
 year = {2025}
}

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TY  - JOUR
T1  - Non-annual Nothobranchiid (Cyprinodontiformes) Growth Type and Health in Southern Cameroon Rainforest Streams: Perspectives from Condition Indices

AU  - Françoise Danielle Messu-Mandeng
AU  - Charles Felix Bilong-Bilong
AU  - Jean-François Agnèse
Y1  - 2025/06/23
PY  - 2025
N1  - https://doi.org/10.11648/j.ijnrem.20251002.18
DO  - 10.11648/j.ijnrem.20251002.18
T2  - International Journal of Natural Resource Ecology and Management
JF  - International Journal of Natural Resource Ecology and Management
JO  - International Journal of Natural Resource Ecology and Management
SP  - 143
EP  - 154
PB  - Science Publishing Group
SN  - 2575-3061
UR  - https://doi.org/10.11648/j.ijnrem.20251002.18
AB  - Understanding population dynamics involves key variables like growth type and body condition, the latter indicating energy acquisition, foraging behaviour, and prey availability, factors influencing species growth, reproduction, fitness, and survival in their habitat. Therefore, using accurate fish condition indices is essential. This study examined the length-weight relationships of 1010 cyprinodontiform individuals from 12 species of non-annual nothobranchiids in southern Cameroon rainforest streams and their well-being using Fulton (Kc), allometric (Ka), and relative weight (Kn) condition factors. Species differed significantly in length (F = 56.79, df = 11, p F = 46.66, df = 11, p p R² ranging from 0.808 to 0.965); three species exhibited positive allometric growth (b > 3) and tended to be thicker, while the other species had negative allometric growth (b Kc values consistently below 1.0, a range proposed to be that of this fish family and not necessarily indicating a poor fish condition. Mean Ka values indicated varying feeding intensities among species, ranging from 0.29 ± 0.01 to 7.63 ± 0.21, and influenced by b-values. Mean Kn values were always greater than 1.0 across all nothobranchiids, not differing among them and reflecting good growth conditions. The study provides first insights into the growth patterns and health of the nothobranchiids within their unique ecosystem, highlighting the advantage of using multiple condition factors to describe species' physiological and ecological well-being and offering essential perspectives for sustainable management and biodiversity conservation efforts.
VL  - 10
IS  - 2
ER  -

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