Abstract
Knowledge of the length at first maturity (L50) is an important tool for fish stock management and conservation. This study estimated the L50 values of 10 fish species in two reservoirs of the Apodi/Mossoró River in the tropical semiarid region of Brazil. The following species were studied: Curimatella lepidura (Eigenmann et Eigenmann, 1889); Prochilodus brevis Steindachner, 1875; Leporinus piau Fowler, 1941; Leporinus taeniatus Lütken 1875; Triportheus signatus (Garman, 1890); Hoplias malabaricus (Bloch, 1794); Hypostomus pusarum (Starks, 1913); Loricariichthys derbyi Fowler, 1915; Trachelyopterus galeatus (Linnaeus, 1766); Crenicichla menezesi Ploeg, 1991. The captured individuals were identified, separated by species, measured for total length (TL), and categorized as reproductive or immature after dissection. The L50 values for both sexes were estimated via a logistic regression for each species. Significant differences between values were tested for the species that occurred in both reservoirs (ANCOVA). The estimated L50 value varied between 7.37 cm (C. lepidura, female) and 19.40 cm (H. malabaricus, female). Only the L50 value of the males of the species C. lepidura and P. brevis differed between the two reservoirs. This study is the first report of the L50 for seven species and the first report for tropical semiarid river basins for two species. These results are important for fish resource management and species conservation.
Highlights
The length at first maturity (L50) is the value at which50% of the individuals in a cohort have reproduced at least once (Barzotto and Mateus 2017), and it represents a critical life cycle transition since the resources and time that were previously solely allocated for growth and survival are used for reproduction (Wootton 1998)
All collected fish were euthanized with a solution of 0.2 mL of clove oil dissolved in 500 mL of water, stored in labelled plastic bags, and transported to the laboratory where they were identified, and their total length (TL) and total weight (TW) were determined
The number of specimens analysed per species ranged from 106 for Hoplias malabaricus to 1754 for Curimatella lepidura, both of which were in the Pau dos Ferros reservoir
Summary
50% of the individuals in a cohort have reproduced at least once (Barzotto and Mateus 2017), and it represents a critical life cycle transition since the resources and time that were previously solely allocated for growth and survival are used for reproduction (Wootton 1998). This very flexible reproductive characteristic exhibits high spatial variation resulting from different responses to local environmental conditions as well as variations in the growth rate, maximum body size, and biotic interactions (Sharpe and Hendry 2009, Lourenço et al 2015). In the course of this study the following species were studied: Curimatella lepidura (Eigenmann et Eigenmann, 1889); Prochilodus brevis Steindachner, 1875; Leporinus piau Fowler, 1941; Leporinus taeniatus Lütken 1875; Triportheus signatus (Garman, 1890); Hoplias malabaricus (Bloch, 1794); Hypostomus pusarum (Starks, 1913); Loricariichthys derbyi Fowler, 1915; Trachelyopterus galeatus (Linnaeus, 1766); Crenicichla menezesi Ploeg, 1991
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