Fellipe Manoel de Sousa França^1,2 and Éder André Gubiani^1,3,4

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Abstract

Length-weight (LWR) and length-length (LLR) relationships were estimated for 51 freshwater fish species caught in the lower Araguaia River, Tocantins-Araguaia basin, Tocantins State, Brazil. Sampling was conducted from March to September 2009 at seven sites along the main river channel. Significant differences in LWR between sexes were found in nine fish species. Isometric growth (b = 3) was observed in 21 fish species. The average b-value was 2.95 (SE = ± 0.05). The average b-value for LLR was 1.158 (SE = ± 0.018). Significant differences in LLR between sexes were found in seven fish species. In four species, females were larger than males of the same species. This study provides the first references for LWR and LLR in nine and 12 fish species, respectively, as well as new maximum total lengths for 15 species. These parameter estimates can be used to assess species conservation status and to develop models of fish growth, reproduction, and fisheries management.

Keywords: Allometry, Ichthyofauna, Individual growth models, Large river, Population structure.

Relações peso-comprimento (RPC) e comprimento-comprimento (RCC) foram estimadas para 51 espécies de peixes capturadas no baixo rio Araguaia, bacia do rio Tocantins-Araguaia, no estado do Tocantins, Brasil. Amostragens foram realizadas de março a setembro de 2009 em sete locais no canal principal do rio. Para nove espécies de peixes diferenças significativas foram registradas para RPC entre os sexos. Vinte e uma espécies apresentaram crescimento isométrico (b = 3). A média do valor de b foi 2,95 (EP = ± 0,05). A média do valor de b na RCC foi de 1,158 (EP = ± 0,018). Para sete espécies de peixes diferenças significativas na RCC foram observadas entre os sexos. Em quatro espécies as fêmeas apresentaram maiores valores de comprimento quando comparadas aos machos da mesma espécie. Primeiro registro de RPC e RCC são apresentados para nove e 12 espécies de peixes, respectivamente. Além disso, registramos novo tamanho máximo para 15 espécies. As estimativas desses parâmetros podem ser usadas para avaliar o estado de conservação das espécies e podem ser usadas para desenvolver modelos de crescimento, reprodução e manejo pesqueiro.

Palavras-chave: Alometria, Estrutura populacional, Ictiofauna, Modelos de crescimento individual, Rio de grande porte.

Introduction

Studies on the length-weight relationship (hereafter LWR) and length-length relationship (hereafter LLR) are important tools for describing various biological aspects, particularly in fish (Le Cren, 1951; Froese, 2006; Gubiani, Horlando, 2014; Gubiani et al., 2020). Estimating the parameters of LWR and LLR is crucial for assessing fish stocks, fisheries, and environmental monitoring programs, especially in Neotropical aquatic environments (Petrere Jr., 1989; Froese, 2006; Gubiani, Horlando, 2014). In addition, these relationships can be used to estimate fish biomass at a given length, infer life history parameters, and build predictive models for behavior or population dynamics at both the population and community levels (Froese, 2006; Gubiani et al., 2012, 2020; Oliveira et al., 2020).

Estimates of the LWR allow for the indirect determination of weight based on length and vice versa, the analysis of growth patterns through the allometric coefficient, and the assessment of the body condition of sampled fish specimens (Braga, 1993; Agostinho, Gomes, 1997; Lemos et al., 2007; Rêgo et al., 2008; Gubiani et al., 2020). On the other hand, LLRs are used to estimate the maximum length a fish can reach and to assess aspects of population structure (Keast, Webb, 1966; Helfman et al., 1997), such as growth, reproduction, diet, behavior, and resistance to predators (Sinovčić et al., 2004; Nath et al., 2017).

Despite the importance of LWR and LLR, this information is still lacking for most fish species in the lower Araguaia River basin. The Araguaia River basin is known for having the greatest fish diversity in the Cerrado, with more than 300 fish species (Lima et al., 2021). Therefore, we estimated the LWR and LLR for several fish species caught in the lower Araguaia River, Tocantins-Araguaia basin, Tocantins State, Brazil. Locally, many of these species are captured by artisanal fisheries (Zacarkim et al., 2015). Hence, this information is essential for the development of management and sustainable exploitation plans for fish stocks, as well as for supporting species conservation strategies to enable the multiple uses of fish populations in the basin.

Material and methods

Study area. The Araguaia River basin covers a drainage area of approximately 377,000 km², with its sources located in the Caiapó Mountains near Emas National Park in the municipality of Mineiros, Goiás State, Brazil. The Araguaia River is a large Neotropical river, 2,110 km long, flowing through the Tocantins-Araguaia basin in northern Brazil (Latrubesse, Stevaux, 2002). Its hydrographic basin can be divided into upper, middle, and lower sections. The lower section begins at the city of Conceição do Araguaia and ends at its confluence with the Tocantins River, extending 500 km (Fig. 1). This region experiences distinct rainy and dry seasons, with flooding typically starting in October and lasting until April (Aquino et al., 2008).

FIGURE 1| Sampling sites (1 to 7) in the lower Araguaia River, Tocantins-Araguaia basin, Tocantins State, Brazil. AP: Amapá State; BA: Bahia State; MA: Maranhão State; MT: Mato Grosso State; PA: Pará State; PI: Piauí State; TO: Tocantins State.

Sampling. Fish were collected bimonthly from March to September 2009 at seven sites located along the Araguaia River channel (Fig. 1; Tab. S1). The sampled stretch is 140 km from the Araguaia River mouth and covers a 100 km watercourse distance. Despite the geographical proximity of the northern most sites, physical structures (e.g., riffles and rapids) in the river create independent sections, and thus the sampling sites were spaced equidistantly, taking these structures into account. For sampling, a standardized set of five different fishing gears was used at each site to capture as many species and individuals as possible. Gill nets (mesh sizes ranging from 2.4–16 cm between opposite knots), 20 m long and 2 m high, were deployed for 24 h, with catches at 08:00, 16:00 and 22:00. Beach seine nets (20 m long with 5 mm mesh) were used in coastal areas without macrophytes or trunks twice a day, at 15:00 and 22:00. Longlines (20 hooks, size 7/0) and branch baited hooks (15 hooks, size 7/0) baited with fish pieces were set for 24 h, with catches at 08:00, 16:00 and 22:00 in lotic zones. Cast nets (10 m²) were thrown 10 times during sunset.

The captured fish were anesthetized and euthanized using an overdose of benzocaine solution (250 mg/l; AVMA, 2001) according to the procedures recommended by ethical guidelines (CFMV, 2002). Afterward, the fish were placed in labeled plastic bags containing 10% formaldehyde and packed in polyethylene containers for preservation and transport to the laboratory. In the laboratory, the specimens were identified according to Santos et al. (2004) and Melo et al. (2005), after which they were measured (total length, TL; standard length, SL, to the nearest 0.1 cm) and weighed (total weight, TW, to the nearest 0.01 g). Additionally, the sex and gonadal development stages of each individual were determined following Vazzoler (1996) and Brown-Peterson et al. (2011) via macroscopic visual inspection of the gonads. Voucher specimens (see Tab. S2) were preserved in 70% alcohol and deposited in the Ichthyological Collection of GERPEL (CIG) at the Universidade Estadual do Oeste do Paraná, Campus Toledo, and in the Ichthyological Collection of the Nupelia (NUP) at the Universidade Estadual de Maringá.

Data analyses. Length-weight relationships (LWRs) were determined using the equation TW = a*SL^b (Ricker, 1973), and length-length relationships (LLRs) were estimated using the equation TL = a + b*SL, based on a linear regression model using the least-squares method (Zar, 1999). For LWRs, the variables TW and SL were log₁₀-transformed (log₁₀TW = log₁₀a + b*log₁₀SL) to achieve linearization. Scatter plots were created for visual inspection of outliers, and extreme outliers (absolute value of standardized residuals ≥ 4) were excluded prior to regression analysis. The goodness of fit for the models was assessed using the coefficient of determination (r²), and the confidence intervals (± 0.95; α = 0.05) for parameters a and b were also estimated for each relationship. A Student’s t-test (Zar, 1999) was used to test for significant differences from the isometric condition (b = 3 for LWRs). Analysis of covariance (ANCOVA; Goldberg, Scheiner, 1993) was used to test for differences between parameters adjusted for males and females for both LWR and LLR. If ANCOVA showed significant differences, LWR and LLR were adjusted separately for each sex; if not, parameters were presented for both sexes combined (denoted as B in the tables). For all analyses, the assumptions of homoscedasticity and/or normality of residuals were evaluated, and if they were not met, the data were transformed (e.g., log, square root, rank; Quinn, Keough, 2002), and parametric analyses were applied to the transformed data (Conover, Iman, 1981), with assumptions checked again. If assumptions were still not met, bootstrap methods were used to test differences between means (Quinn, Keough, 2002). All statistical analyses were performed using R software (R Development Core Team, 2024). The significance level for all analyses was set at p < 0.05.

Results

A total of 4,525 individuals were caught, comprising 1,479 males and 1,308 females. For 1,738 specimens, it was not possible to determine sex through macroscopic inspection of the gonads. These individuals belonged to 51 fish species distributed across five orders, 19 families, and 43 genera (Tab. S2). Length-weight relationship adjustments were made for all recorded species (Tab. 1; Fig. S3). After excluding outliers and specimens whose sex could not be identified, 4,139 individuals were used to fit the LWR (Tab. 1; Fig. S3). The total number of individuals per species ranged from four for males of Loricaria cataphracta Linnaeus, 1758, to 249 individuals of Poptella cf. compressa (Günther, 1864) (Tab. 1). The smallest recorded standard length was 1.10 cm for Satanoperca acuticeps (Heckel, 1840), while the largest was 21.90 cm for Hydrolycus armatus (Jardine, 1841) (Tab. 1). New maximum total lengths were reported for 15 fish species (Tab. 2; values in bold), based on information available in FishBase (Froese, Pauly, 2024). The lowest total weight was 0.02 g for S. acuticeps, and the highest was 2,750.00 g for H. armatus (Tab. 1). The LWR of nine fish species differed significantly between the sexes (ANCOVA; p < 0.05; Tab. 1).

TABLE 1 | Descriptive statistics and estimated parameters of length-weight relationships for 51 fish species captured in the lower Araguaia River, Tocantins-Araguaia basin, Tocantins State, Brazil, from March to September 2009. (B) Both sexes, (M) males, (F) females, (N) total fish caught, (Min) minimum value reported, (Max) maximum value reported, (a) intercept, (b) slope, (CI) confidence interval, (SE) standard error, (r²) coefficient of determination, and *indicate the first report of LWR according to FishBase.

			Length characteristics (cm)		Weight characteristics (g)									t-test (H₀=3)
Species	Sex	N	Min	Max	Min	Max	a	95% CI a	SE a	b	95% CI b	SE b	r²	t_0.05	p-value	Growth type
Acestrorhynchus microlepis	B	77	6.00	22.00	2.24	121.80	0.014	0.001-0.019	0.072	2.91	2.78-3.04	0.065	0.96	-1.398	0.166	Isometric
Ageneiosus inermis	B	70	15.70	51.00	29.10	2060.00	0.007	0.003-0.016	0.171	3.20	2.97-3.43	0.116	0.92	1.716	0.091	Isometric
Ageneiosus ucayalensis	B	146	9.70	28.50	8.40	205.60	0.008	0.005-0.012	0.096	3.07	2.92-3.23	0.078	0.92	0.926	0.356	Isometric
Agoniates halecinus	F	27	13.00	20.20	22.00	78.50	0.064	0.011-0.365	0.366	2.31	1.69-2.93	0.300	0.70	-2.293	0.031	Allometric (-)
	M	40	9.50	19.00	7.50	64.10	0.016	0.006-0.041	0.205	2.78	2.44-3.13	0.172	0.87	-1.243	0.220	Isometric
Aphanotorulus emarginatus*	F	63	4.20	27.30	1.66	381.60	0.037	0.028-0.049	0.059	2.73	2.63-2.82	0.048	0.98	-5.703	0.001	Allometric (-)
	M	97	4.50	34.70	2.20	543.60	0.040	0.033-0.049	0.043	2.72	2.65-2.78	0.034	0.98	-8.267	0.001	Allometric (-)
Auchenipterichthys coracoideus	F	72	5.70	8.30	4.51	15.30	0.147	0.066-0.329	0.175	2.06	1.63-2.48	0.211	0.58	-4.476	0.001	Allometric (-)
	M	134	5.50	10.20	4.28	26.80	0.060	0.038-0.093	0.098	2.54	2.31-2.77	0.116	0.78	-3.976	0.001	Allometric (-)
Auchenipterus nuchalis	B	71	10.50	17.50	11.60	75.40	0.004	0.002-0.007	0.131	3.39	3.17-3.62	0.113	0.93	3.467	0.001	Allometric (+)
Auchenipterus osteomystax	F	16	12.90	17.70	25.00	68.30	0.149	0.009-2.401	0.562	2.01	0.98-3.02	0.473	0.56	-2.092	0.055	Isometric
	M	18	12.90	32.00	23.70	479.40	0.007	0.002-0.022	0.246	3.18	2.74-3.62	0.206	0.94	0.869	0.397	Isometric
Baryancistrus niveatus	B	82	5.00	23.20	3.91	500.60	0.022	0.018-0.027	0.046	3.16	3.08-3.24	0.040	0.99	4.114	0.001	Allometric (+)
Bivibranchia cf. notata*	B	112	1.30	16.00	0.05	57.60	0.012	0.010-0.013	0.025	3.14	3.05-3.24	0.048	0.97	2.959	0.004	Allometric (+)
Bivibranchia velox	B	35	1.80	5.70	0.12	2.80	0.021	0.018-0.025	0.039	2.72	2.60-2.85	0.061	0.98	-4.552	0.001	Allometric (-)
Boulengerella cuvieri	B	151	10.80	50.00	7.90	1150.00	0.002	0.001-0.002	0.065	3.42	3.33-3.51	0.045	0.97	9.441	0.001	Allometric (+)
Bryconops alburnoides	B	195	1.80	11.60	0.11	25.40	0.015	0.014-0.016	0.013	2.95	2.92-2.98	0.015	0.99	-3.113	0.002	Allometric (-)
Caenotropus labyrinthicus	B	79	7.50	19.00	10.30	108.30	0.031	0.018-0.053	0.117	2.89	2.67-3.11	0.111	0.90	-1.005	0.318	Isometric
Cetopsis coecutiens	B	83	10.40	26.00	19.00	377.80	0.023	0.015-0.037	0.097	2.97	2.81-3.14	0.083	0.94	-0.324	0.747	Isometric
Chalceus macrolepidotus	B	51	6.70	12.50	6.10	47.90	0.012	0.007-0.020	0.114	3.27	3.05-3.50	0.112	0.94	2.444	0.018	Allometric (+)
Cichla piquiti	B	31	8.40	39.80	15.40	1820.00	0.019	0.012-0.029	0.090	3.08	2.95-3.21	0.063	0.99	1.250	0.221	Isometric
Curimata inornata	B	64	6.00	21.50	6.70	292.90	0.023	0.019-0.029	0.050	3.09	3.01-3.19	0.047	0.99	2.012	0.048	Allometric (+)
Cyphocharax plumbeus	B	192	2.70	9.80	0.53	30.30	0.025	0.021-0.028	0.030	3.10	3.02-3.18	0.042	0.97	2.406	0.017	Allometric (+)
Exodon paradoxus*	B	51	3.30	6.50	0.95	9.00	0.022	0.017-0.029	0.059	3.20	3.03-3.37	0.085	0.97	2.400	0.021	Allometric (+)
Hassar wilderi	B	111	10.90	27.60	16.90	256.30	0.082	0.024-0.282	0.269	2.46	2.02-2.91	0.225	0.52	-2.376	0.019	Allometric (-)
Hemiodus cf. unimaculatus	F	63	8.00	18.00	9.40	135.40	0.010	0.007-0.014	0.074	3.22	3.08-3.35	0.068	0.97	3.230	0.002	Allometric (+)
	M	92	7.00	20.00	5.60	169.30	0.021	0.015-0.028	0.066	2.93	2.81-3.05	0.062	0.96	-1.107	0.271	Isometric
Hydrolycus armatus	B	44	21.90	56.00	165.60	2750.00	0.008	0.003-0.022	0.209	3.20	2.91-3.48	0.141	0.92	1.408	0.166	Isometric
Laemolyta fernandezi	B	50	7.80	20.00	8.20	194.90	0.010	0.006-0.017	0.121	3.19	2.97-3.41	0.108	0.95	1.759	0.085	Isometric
Leporinus affinis	B	63	8.20	27.40	9.40	441.30	0.013	0.010-0.017	0.061	3.14	3.05-3.24	0.049	0.98	2.931	0.005	Allometric (+)
Leporinus maculatus	B	35	7.50	12.50	7.60	38.30	0.020	0.012-0.032	0.101	2.99	2.78-3.20	0.104	0.96	-0.075	0.941	Isometric
Leporinus unitaeniatus*	B	34	7.70	17.20	7.40	177.80	0.006	0.003-0.012	0.161	3.44	3.12-3.76	0.158	0.94	2.786	0.009	Allometric (+)
Limatulichthys griseus	B	49	1.50	17.30	0.07	33.70	0.007	0.006-0.008	0.038	2.83	2.73-2.94	0.052	0.98	-3.157	0.003	Allometric (-)
Loricaria cataphracta	F	10	11.50	20.40	9.90	53.00	0.010	0.003-0.031	0.210	2.83	2.44-3.21	0.168	0.97	-1.031	0.333	Isometric
	M	4	10.70	20.00	7.20	46.90	0.006	0.001-0.144	0.325	2.97	1.79-4.16	0.276	0.98	-0.088	0.937	Isometric
Moenkhausia cf. lepidura	B	96	1.90	5.70	0.23	4.24	0.023	0.019-0.028	0.041	2.93	2.80-3.05	0.063	0.96	-1.185	0.239	Isometric
Moenkhausia dichroura	B	86	1.70	6.30	0.12	4.80	0.009	0.005-0.015	0.120	3.44	3.08-3.81	0.184	0.81	2.416	0.018	Allometric (+)
Moenkhausia gracilima*	B	74	1.60	3.30	0.09	0.57	0.028	0.020-0.037	0.069	2.63	2.26-2.99	0.182	0.74	-2.054	0.044	Allometric (-)
Myloplus torquatus	B	30	1.30	11.00	0.10	61.30	0.075	0.062-0.091	0.040	2.83	2.66-3.01	0.085	0.97	-1.950	0.061	Isometric
Pachyurus junki	B	41	7.00	25.00	8.80	313.10	0.021	0.013-0.034	0.105	2.94	2.77-3.11	0.084	0.97	-0.728	0.471	Isometric
Peckoltia vittata	B	58	4.90	17.50	4.11	178.70	0.049	0.040-0.061	0.045	2.84	2.74-2.94	0.051	0.98	-3.094	0.003	Allometric (-)
Pimelodus cf. blochii	B	99	7.50	20.20	7.50	168.20	0.018	0.012-0.025	0.077	3.00	2.86-3.14	0.069	0.95	-0.003	0.998	Isometric
Pinirampus pirinampu	F	12	17.00	51.50	57.40	2010.00	0.011	0.003-0.040	0.252	3.07	2.71-3.43	0.160	0.97	0.441	0.668	Isometric
	M	17	11.60	54.00	16.40	2380.00	0.007	0.006-0.009	0.051	3.15	3.08-3.22	0.034	1.00	4.394	0.001	Allometric (+)
Plagioscion squamosissimus	B	61	8.60	36.00	14.30	1050.00	0.019	0.011-0.035	0.128	3.02	2.83-3.20	0.093	0.95	0.165	0.869	Isometric
Poptella cf. compressa	B	249	3.20	4.70	0.78	3.08	0.052	0.035-0.076	0.086	2.50	2.20-2.80	0.151	0.52	-3.325	0.001	Allometric (-)
Pristigaster cayana	F	38	10.80	15.00	19.60	59.50	0.013	0.005-0.035	0.207	3.08	2.70-3.46	0.188	0.88	0.406	0.687	Isometric
	M	25	10.00	15.70	17.00	56.40	0.134	0.023-0.792	0.373	2.14	1.43-2.85	0.342	0.63	-2.514	0.019	Allometric (-)
Rhaphiodon vulpinus	B	57	14.00	47.00	14.90	850.00	0.001	0.001-0.004	0.257	3.50	3.16-3.83	0.166	0.89	2.995	0.004	Allometric (+)
Roeboides affinis	B	77	4.70	10.10	1.45	16.90	0.009	0.007-0.012	0.052	3.25	3.13-3.37	0.062	0.97	4.002	0.001	Allometric (+)
Satanoperca acuticeps	B	95	1.10	15.30	0.02	136.40	0.019	0.018-0.021	0.018	3.29	3.23-3.34	0.028	0.99	10.290	0.001	Allometric (+)
Serrapinnus cf. kriegi*	B	35	1.30	3.10	0.04	0.57	0.017	0.011-0.028	0.101	2.83	2.15-3.52	0.337	0.68	-0.500	0.620	Isometric
Serrasalmus maculatus	B	72	4.90	21.50	2.84	396.60	0.018	0.014-0.022	0.047	3.23	3.14-3.32	0.043	0.99	5.367	0.001	Allometric (+)
Steindachnerina amazonica*	B	47	3.50	6.00	1.06	4.59	0.041	0.030-0.055	0.067	2.71	2.50-2.91	0.103	0.94	-2.860	0.006	Allometric (-)
Sturisoma rostratum*	F	27	17.00	22.30	20.40	47.80	0.040	0.001-1.311	0.735	2.28	1.11-3.44	0.567	0.39	-1.277	0.213	Isometric
	M	29	18.50	21.70	27.50	54.90	0.003	0.001-0.018	0.405	3.21	2.56-3.84	0.312	0.80	0.658	0.516	Isometric
Tenellus leporhinus*	B	33	9.40	18.50	14.00	86.20	0.090	0.025-0.332	0.272	2.30	1.80-2.81	0.247	0.74	-2.818	0.008	Allometric (-)
Tetragonopterus argenteus	B	31	4.50	7.20	2.22	16.80	0.023	0.009-0.058	0.175	3.28	2.70-3.86	0.284	0.82	0.987	0.332	Isometric
Tetragonopterus chalceus	B	34	3.70	8.60	1.55	30.00	0.019	0.013-0.027	0.171	3.42	3.21-3.63	0.105	0.97	3.995	0.001	Allometric (+)
Triportheus albus	B	204	1.60	23.00	0.06	180.40	0.019	0.018-0.020	0.010	2.90	2.87-2.93	0.016	0.99	-6.319	0.001	Allometric (-)

TABLE 2 | Descriptive statistics and estimated parameters of length-length relationships for 51 fish species captured in the lower Araguaia River, Tocantins-Araguaia basin, Tocantins State, Brazil, from March to September 2009. (B) Both sexes, (M) males, (F) females, (N) total fish caught, (Min) minimum value reported, (Max) maximum value reported, (a) intercept, (b) slope, (CI) confidence interval, (SE) standard error, (r²) coefficient of determination. Values in bold indicate the new maximum total length according to FishBase, and *indicate the first report of LLR according to FishBase.

			Total length characteristics (cm)		Standard length characteristics (cm)
Species	Sex	N	Min	Max	Min	Max	a	95% CI a	SE a	b	95% CI b	SE b	r²
Acestrorhynchus microlepis	F	28	9.60	25.00	8.00	22.00	0.732	0.188-1.276	0.265	1.115	1.076-1.153	0.019	0.99
	M	29	11.70	24.40	10.00	20.60	-0.151	-0.663-0.362	0.250	1.182	1.142-1.221	0.019	0.99
Ageneiosus inermis	F	36	19.20	57.00	15.70	51.00	2.149	1.170-3.128	0.482	1.076	1.046-1.106	0.015	0.99
	M	21	21.20	48.00	17.20	44.00	3.934	1.859-6.010	0.991	0,998	0.926-1.070	0.034	0.98
Ageneiosus ucayalensis	B	147	12.00	34.00	9.70	28.50	1.109	0.558-1.660	0.279	1.140	1.109-1.172	0.016	0.97
Agoniates halecinus	B	76	10.50	25.50	8.60	20.20	0.745	0.026-1.464	0.361	1.144	1.100-1.189	0.022	0.97
Aphanotorulus emarginatus*	B	177	5.50	44.70	4.20	34.70	0.044	-0.423-0.512	0.237	1.306	1.281-1.331	0.013	0.98
Auchenipterichthys coracoideus*	B	227	4.70	13.20	3.90	10.90	0.495	0.157-0.833	0.172	1.169	1.121-1.218	0.025	0.91
Auchenipterus nuchalis	B	72	11.90	20.60	10.50	17.50	0.895	-0.019-1.809	0.458	1.099	1.036-1.162	0.032	0.94
Auchenipterus osteomystax	B	39	13.20	36.50	10.00	32.00	0.987	0.383-1.590	0.298	1.111	1.074-1.148	0.018	0.99
Baryancistrus niveatus	F	18	9.30	28.90	7.00	23.20	1.748	0.280-3.216	0.692	1.142	1.058-1.227	0.040	0.98
	M	18	8.30	28.00	6.40	23.00	1.187	0.007-2.368	0.557	1.207	1.136-1.278	0.033	0.99
Bivibranchia cf. notata*	B	110	1.80	18.80	1.30	16.00	0.133	0.090-0.177	0.022	1.184	1.173-1.195	0.005	0.99
Bivibranchia velox	B	34	2.60	7.00	1.80	5.70	0.279	0.101-0.457	0.087	1.169	1.128-1.209	0.020	0.99
Boulengerella cuvieri	B	146	13.30	57.00	10.80	50.00	1.839	1.365-2.313	0.240	1.097	1.082-1.112	0.008	0.99
Bryconops alburnoides	B	194	2.20	15.00	1.80	11.60	0.021	-0.062-0.103	0.042	1.236	1.226-1.245	0.005	0.99
Caenotropus labyrinthicus	B	67	9.40	24.80	7.50	19.00	-0.476	-1.098-0.146	0.312	1.262	1.208-1.315	0.027	0.97
Cetopsis coecutiens	B	78	12.90	31.20	10.40	26.00	0.467	0.012-0.923	0.229	1.171	1.141-1.202	0.015	0.99
Chalceus macrolepidotus	B	46	8.20	15.70	6.70	12.50	0.730	-0.207-1.666	0.465	1.186	1.096-1.277	0.045	0.94
Cichla piquiti	F	12	16.70	46.80	13.70	39.80	0.187	-1.675-2.050	0.836	1.196	1.131-1.262	0.029	0.99
	M	12	23.90	47.40	20.00	39.80	0.257	-0.484-0.999	0.333	1.177	1.154-1.200	0.010	0.99
Curimata inornata	B	59	7.90	27.20	6.00	21.50	0.481	-0.015-0.977	0.248	1.234	1.193-1.274	0.020	0.98
Cyphocharax plumbeus*	B	173	3.40	10.00	2.50	7.90	0.276	0.116-0.436	0.081	1.248	1.216-1.280	0.016	0.97
Exodon paradoxus	B	52	4.10	10.10	3.30	8.40	0.582	0.323-0.842	0.129	1.152	1.102-1.202	0.025	0.98
Hassar wilderi*	B	110	12.50	24.30	10.90	27.60	2.487	1.546-3.429	0.475	1.037	0.977-1.097	0.030	0.91
Hemiodus cf. unimaculatus	B	168	9.00	24.50	7.00	20.00	0.268	0.026-0.511	0.123	1.222	1.202-1.241	0.010	0.99
Hydrolycus armatus	F	13	27.30	60.00	22.80	56.00	3.846	1.928-5.765	0.872	1.017	0.961-1.073	0.025	0.99
	M	20	26.40	48.40	21.90	41.00	1.416	-0.741-3.572	1.027	1.118	1.047-1.189	0.034	0.98
Laemolyta fernandezi	B	44	9.60	23.50	7.80	20.00	1.466	0.902-2.030	0.279	1.106	1.065-1.147	0.020	0.99
Leporinus affinis	B	53	9.60	32.00	8.20	27.40	1.375	0.762-1.988	0.305	1.128	1.095-1.160	0.016	0.99
Leporinus maculatus	B	32	9.50	15.40	7.50	12.50	0.730	0.287-1.172	0.217	1.174	1.128-1.219	0.022	0.99
Leporinus unitaeniatus*	B	29	9.80	20.40	7.70	17.20	1.131	0.392-1.871	0.360	1.116	1.048-1.184	0.033	0.98
Limatulichthys griseus	B	49	1.70	21.10	1.50	17.30	-0.027	-0.099-0.046	0.036	1.128	1.116-1.139	0.006	0.99
Loricaria cataphracta*	F	10	15.70	22.90	11.50	20.40	6.822	0.998-12.645	2.525	0.771	0.448-1.094	0.140	0.79
	M	4	12.50	28.90	10.70	20.00	-8.163	-28.914-12.588	4.823	1.787	0.450-3.123	0.310	0.94
Moenkhausia cf. lepidura	B	89	3.10	7.20	2.30	5.70	0.223	0.047-0.399	0.088	1.215	1.176-1.254	0.019	0.98
Moenkhausia dichroura	B	73	1.50	7.30	1.70	6.30	2.578	1.741-3.415	0.420	0.693	0.506-0.879	0.093	0.43
Moenkhausia gracilima*	B	63	2.10	4.10	1.60	3.30	0.187	-0.001-0.375	0.094	1.170	1.091-1.249	0.039	0.93
Myloplus torquatus*	B	30	1.70	14.50	1.30	11.00	-0.044	-0.14-0.052	0.047	1.321	1.297-1.344	0.011	0.99
Pachyurus junki	B	36	12.00	29.70	9.40	25.00	0.870	0.319-1.422	0.271	1.165	1.136-1.194	0.014	0.99
Peckoltia vittata	B	58	6.50	22.70	4.90	17.50	-0.023	-0.315-0.269	0.146	1.333	1.299-1.366	0.017	0.99
Pimelodus cf. blochii	F	20	11.00	19.10	8.80	15.70	1.210	-0.177-2.596	0.660	1.117	1.014-1.220	0.049	0.97
	M	68	9.40	22.90	7.50	18.00	0.793	0.102-1.485	0.346	1.170	1.119-1.221	0.026	0.97
Pinirampus pirinampu	B	26	14.30	58.00	11.50	51.50	3.804	1.789-5.819	0.976	1.060	1.000-1.120	0.029	0.98
Plagioscion squamosissimus	B	55	10.70	43.00	8.60	36.00	1.351	0.517-2.184	0.415	1.158	1.124-1.193	0.017	0.99
Poptella cf. compressa	B	240	3.10	6.20	3.20	4.70	0.587	0.281-0.893	0.155	1.130	1.047-1.212	0.042	0.75
Pristigaster cayana	B	78	13.10	34.50	10.00	28.70	2.535	1.565-3.505	0.487	1.097	1.024-1.171	0.037	0.92
Rhaphiodon vulpinus	B	48	15.60	48.80	14.00	43.50	2.182	0.666-3.698	0.753	1.057	1.015-1.099	0.021	0.98
Roeboides affinis*	B	77	5.80	12.20	4.70	10.10	0.306	0.061-0.552	0.123	1.176	1.141-1.211	0.018	0.98
Satanoperca acuticeps	B	91	1.40	19.50	1.10	15.30	-0.023	-0.092-0.046	0.035	1.273	1.263-1.284	0.005	0.99
Serrapinnus cf. kriegi	B	34	1.60	3.90	1.30	3.10	0.114	-0.073-0.301	0.092	1.169	1.077-1.261	0.045	0.95
Serrasalmus maculatus	B	72	6.30	25.20	4.90	21.50	0.704	0.361-1.046	0.172	1.154	1.129-1.180	0.013	0.99
Steindachnerina amazonica*	B	46	4.60	7.70	3.50	6.00	0.560	0.309-0.811	0.124	1.195	1.140-1.251	0.027	0.98
Sturisoma rostratum*	B	75	9.50	27.00	8.20	22.70	0.111	-0.736-0.959	0.425	1.143	1.097-1.189	0.023	0.97
Tenellus leporhinus	B	33	11.40	21.50	9.40	18.50	1.081	0.130-2.032	0.466	1.107	1.033-1.180	0.036	0.97
Tetragonopterus argenteus	B	29	6.00	9.20	4.50	7.20	0.594	-0.001-1.082	0.286	1.182	1.067-1.296	0.056	0.94
Tetragonopterus chalceus	B	32	4.80	11.20	3.70	8.60	0.267	-0.052-0.587	0.156	1.240	1.185-1.294	0.027	0.99
Triportheus albus	B	196	2.10	25.70	1.60	23.00	0.136	0.102-0.170	0.017	1.206	1.201-1.212	0.003	0.99

All LWR adjustments were significant (p < 0.01). A new LWR was reported for nine fish species (Tab. 1; values marked with asterisks). The estimated values for parameter b ranged from 2.01 for females of Auchenipterus osteomystax (Miranda Ribeiro, 1918) to 3.50 for Rhaphiodon vulpinus Spix & Agassiz, 1829 (Tab. 1). The average b-value was 2.95 (SE = ^± 0.05), and the median b-value was 3.00, with 50% of the values ranging from 2.82 to 3.20. Only 19 fish species exhibited isometric growth (b = 3; p > 0.05; Tab. 1; Fig. S3). Additionally, males of Agoniates halecinus Müller & Troschel, 1845, and females of Pinirampus pirinampu (Spix & Agassiz, 1829) and Pristigaster cayana Cuvier, 1829, also exhibited isometric growth (Tab. 1; Fig. S3). The r² value ranged from 0.39 for females of Sturisoma rostratum (Spix & Agassiz, 1829) to 1.00 for males of P. pirinampu (Tab. 1; Fig. S3).

After excluding outliers, 3,972 individuals were used to fit the LLR (Tab. 2; Fig. S4). The number of individuals per species ranged from four males of Loricaria cataphracta to 240 individuals of Poptella cf. compressa (Tab. 2). The minimum recorded total length was 1.40 cm for Satanoperca acuticeps (Tab. 2; Fig. S4), while the maximum was 60.00 cm for females of Hydrolycus armatus (Tab. 2; Fig. S4). Similarly, the minimum recorded standard length was 1.10 cm for S. acuticeps (Tab. 2; Fig. S4), and the maximum was 56.00 cm for females of H. armatus (Tab. 2; Fig. S4). New maximum total lengths were reported for 15 fish species (Tab. 2) based on information available in FishBase (Froese, Pauly, 2024).

All LLR fits were significant (p < 0.05). A new LLR was reported for 12 fish species (Tab. 2; values marked with asterisks). The estimated value for parameter b ranged from 0.693 for Moenkhausia dichroura (Kner, 1858)to 1.787 for males of Loricaria cataphracta (Tab. 2). The average b-value was 1.158 (SE = ± 0.018), with a median of 1.167, and 50% of the values ranging from 1.115 to 1.196. The a intercept value was not significant for 20 of the fits (confidence interval included zero; Tab. 2). The r² value ranged from 0.43 for M. dichroura to 0.99 for 26 of the fits (see Tab. 2). A significant difference in the LLR was detected between the sexes for seven fish species (ANCOVA; p < 0.05; Tab. 2; Fig. S4). For most species, females were larger than males of the same species (Tab. 2; Fig. S4).

Discussion

Our results indicated that the b-values for the length-weight relationship ranged from 2.01 to 3.50. According to Tesch (1971), estimates for parameter b typically center around three for fish, with a range from two to four. Thus, our findings align with this expected variability, where, of the 51 adjustments, 19 exhibited isometric growth (b = 3; Tab. 1). This consistency in b-value has been observed across many fish species in various aquatic environments. For example, in a review of the length-weight relationship in fish, Froese (2006) noted that most b-values fell within the range of 2.5 < b < 3.5. Similarly, Giarrizzo et al. (2011) estimated b-values for 27 fish species from the Trombetas River in Pará State, Brazil, with values ranging from 2.51 to 3.49. More recently, Genovai et al. (2024) reported length‒weight relationships for 10 fish species from headwater streams in the lower Iguassu River basin, with b-values ranging from 2.37 to 3.62. These studies, along with many others (Gubiani, Horlando, 2014; Cella-Ribeiro et al., 2015; Giarrizzo et al., 2015; Nobile et al., 2015; Freitas et al., 2017; Lubich et al., 2021; Olentino et al., 2023), have demonstrated that the variation pattern for b-values consistently falls between two and four.

As previously mentioned, 19 (37%) fish species exhibited isometric growth, which reflects growth rates in weight and length that are similar across different parts of the body (Benedito-Cecílio, Agostinho, 1997). Similarly, Giarrizzo et al. (2015), who estimated the length-weight relationship for 135 fish species from the Xingu River, Amazon basin, Brazil, found that 33% of the fish species displayed isometric growth. Likewise, Genovai et al. (2024), who estimated the length-weight relationship for 10 fish species from headwater streams of the lower Iguassu River basin, Brazil, observed that most fish species exhibited isometric growth, a pattern also reported by other authors (Nobile et al., 2015; Camargo et al., 2018; Lubich et al., 2020). In contrast, Gubiani, Horlando (2014), who estimated the length-weight relationship for 20 fish species from the Salto Santiago Reservoir, Iguassu River, Brazil, and Gubiani et al. (2009), who estimated the length-weight relationship for 48 fish species in 30 reservoirs in the state of Paraná, Brazil, observed positive allometric growth in the majority of species. Under these conditions, weight increases more than length, with the b-value exceeding three (Ricker, 1979). In our study, we observed positive allometry in 16 fish species (Tab. 1). Additionally, 12 fish species exhibited negative allometry (b < 3), indicating that length increased more than weight. Finally, we noted differences in growth patterns between sexes for four fish species: females of Agoniates halecinus and males of Pristigaster cayana showed negative allometry, while females of Hemiodus cf. unimaculatus (Bloch, 1794) and males of Pinirampus pirinampu exhibited positive allometric growth. Differences in the length-weight relationship between sexes of the same species are common and can be influenced by various factors, such as resource availability, gastric fullness, gonadal development stage, health, and size variation among captured individuals (Tesch, 1971; Wootton, 1998; Cherif et al., 2008).

Size differences between males and females of the same fish species have been observed for a long time (see Haas, 1976), and this characteristic is one of the drivers of sexual dimorphism. In our study, we recorded differences in the length-weight relationships between sexes for A. halecinus, P. cayana, and Loricaria cataphracta, where females grew larger than males. In contrast, for Aphanotorulus emarginatus (Valenciennes, 1840), Auchenipterichthys coracoideus (Eigenmann & Allen, 1942), Auchenipterus osteomystax, H. cf. unimaculatus, P. pirinampu, and S. rostratum, males grew larger than females. According to Vazzoler (1996), who studied the reproduction of Neotropical fish, females invest more energy in reproduction, which often results in them being larger than males in certain species.

Differences in the length-length relationships between sexes for Acestrorhynchus microlepis (Jardine, 1841), Ageneiosus inermis (Linnaeus, 1766), Cichla piquiti Kullander & Ferreira, 2006, and Hydrolycus armatus showed that females had a longer caudal fin than males, potentially enhancing their swimming ability. In contrast, for Baryancistrus niveatus (Castelnau, 1855), L. cataphracta and Pimelodus cf. blochii Valenciennes, 1840, males had a longer caudal fin than females. According to Rêgo et al. (2008), who studied 29 fish species captured in a newly formed reservoir in Capim Branco city, Minas Gerais State, Brazil, increased caudal fin length is related to sexual attraction, metabolic differences, and, ultimately, greater genetic variability.

In summary, this study provides the first reference on the LWRs of nine fish species, including A. emarginatus, Bivibranchia cf. notata Vari & Goulding, 1985, Exodon paradoxus Müller & Troschel, 1844, Leporinus unitaeniatus Garavello & Santos, 2009, Moenkhausia cf. gracilima Eigenmann, 1908, Serrapinnus cf. kriegi (Schindler, 1937), Steindachnerina amazonica (Steindachner, 1911), S. rostratum, and Tenellus leporhinus (Eigenmann, 1912) (Tab. 1, species marked with an asterisk). It also records new maximum total lengths for 15 fish species (Tab. 2, values in bold) and provides the first reference for LLRs of 12 fish species, including A. emarginatus, A. caracoideus, B. notata, Cyphocharax plumbeus (Eigenmann & Eigenmann, 1889), Hassar wilderi Kindle, 1895, L. unitaeniatus, L. cataphracta, M. gracilima, Myloplus torquatus (Kner, 1858), Roeboides affinis (Günther, 1868), S. amazonica, and S. rostratum (Tab. 2, species marked with an asterisk), based on information available in FishBase (Froese, Pauly, 2024). Estimating parameters of different population structure metrics helps us understand the various growth strategies of individuals and allows us to correlate these variables with environmental, ecological, and physiological factors. These estimates provide important biological information for Neotropical freshwater fishes and will assist in the management of fishery resources and conservation of fish fauna in regions with limited fish data.

Acknowledgments

We thank the technicians of the Grupo de Pesquisas em Recursos Pesqueiros e Limnologia (GERPEL) for their assistance with fieldwork. This study was partially funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES/ Ministério da Educação) – Finance Code 001. This research was conducted under the environmental project of the Santa Isabel Hydroelectric Plant.

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Authors

Fellipe Manoel de Sousa França^1,2 and Éder André Gubiani^1,3,4

^[1] Programa de Pós-Graduação em Conservação e Manejo de Recursos Naturais, Centro de Ciências Biológicas e da Saúde, Universidade Estadual do Oeste do Paraná (UNIOESTE), Campus Cascavel, Rua Universitária, 2069, Bairro Universitário, 85819 110 Cascavel, PR, Brazil. (FMSF) fellipe.franca@live.com, (EAG) eder.gubiani@unioeste.br (corresponding author).

^[2] Coordenação Geral de Proteção (CGPRO), Diretoria de Criação e Manejo de Unidades de Conservação (DIMAN), EQSW 103/104, Complexo Administrativo, Setor Sudoeste, Bloco B, 2° andar, Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio), 70670-350 Brasília, DF, Brazil.

^[3] Programa de Pós-Graduação em Recursos Pesqueiros e Engenharia de Pesca, Centro de Engenharias e Ciências Exatas, Universidade Estadual do Oeste do Paraná (UNIOESTE), Campus Toledo, Rua Guaíra, 3141, Jardim Santa Maria, 85903-220 Toledo, PR, Brazil.

^[4] Laboratório de Ictiologia e Estatística Pesqueira (ICTES), Instituto Neotropical de Pesquisas Ambientais (INEO), Grupo de Pesquisas em Recursos Pesqueiros e Limnologia (GERPEL), Universidade Estadual do Oeste do Paraná (UNIOESTE), Campus Toledo, Rua Guaíra, 3141, Jardim Santa Maria, 85903-220 Toledo, PR, Brazil.

Authors’ Contribution

Fellipe Manoel de Sousa França: Data curation, Formal analysis, Writing-original draft.

Éder André Gubiani: Conceptualization, Data curation, Formal analysis, Methodology, Supervision, Writing-review and editing.

Ethical Statement

Samplings were conducted under IBAMA authorization n° 55/2009 – CGFAP/IBAMA, lawsuit IBAMA n° 02001.001338/2009–41.

Competing Interests

The author declares no competing interests.

How to cite this article

França FMS, Gubiani EA. Length-weight and length-length relationships for freshwater fish species from the lower Araguaia River, Tocantins-Araguaia basin, Tocantins State, Brazil. Neotrop Ichthyol. 2025; 23(1):e240046. https://doi.org/10.1590/1982-0224-2024-0046

Copyright

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Distributed under

Creative Commons CC-BY 4.0

Diversity and Distributions Published by SBI

Accepted January 16, 2025 by Francisco Araújo

Submitted May 23, 2024

Epub March 24, 2025

Abstract​

Introduction​

Material and methods

Results​

Discussion​

Acknowledgments​

References​