Abstract
Simple SummaryThe study of age and growth patterns in skates and rays can be conducted by analyzing mineral deposition patterns inside the vertebrae as biological features may influence age estimation. For the giant electric ray (Narcine entemedor), age was estimated by analyzing the vertebrae and an annual deposition pattern was found. After considering additional biological features such as birth date and date of capture, a more precise description of growth pattern was made. We concluded that this species is a moderate body size elasmobranch with moderate longevity and fast growth. Our results provide useful information for the future management of this exploited species.The age and growth rate of the giant electric ray, Narcine entemedor, was estimated using growth bands deposited in the vertebral centra of 245 specimens. Differences in size and age distribution were found between the sexes, a pattern that suggests the annual deposition of band pairs, possibly occurring in April. Multimodel inference and back-calculation were performed to three age data sets of females considering their reproductive cycle and time of capture, among which the von Bertalanffy growth function was found to be the most appropriate (L∞ = 81.87 cm TL, k = 0.17 year−1). Our research supports the idea that age can be determined via biological features such as birth date and growth band periodicity. We concluded that N. entemedor is of a moderate body size, moderate longevity and is a fast-growing elasmobranch species.
Highlights
Introduction iationsTraditionally, it has been recognized that elasmobranchs, due to their biological characteristics, are especially vulnerable to overfishing [1,2,3,4]
Accounting for this, annual deposition of a pair of bands was assumed in our study; we suggest being cautious since marginal increment ratios (MIR) did not show monthly significant differences
Considering that the rest of the parameters varied slightly between data sets, according to statistical results (–log-likelihood, Akaike’s Information Criterion (AIC) and Wi ) and biological interpretation (L∞, k and L0 values), we considered the VBG-3 based on the adjusted age to date of capture to be the growth model that best describes individual growth of N. entemedor
Summary
Introduction iationsTraditionally, it has been recognized that elasmobranchs, due to their biological characteristics (late maturation, low fecundity, slow growth), are especially vulnerable to overfishing [1,2,3,4]. Evidence has proven that life-history traits of this group may vary between K and r strategies, allowing some species to respond differently to fishing pressure [5,6,7]. In this sense, it is important to understand the life-history parameters of the species, those that are related to the degree of vulnerability and risk to fishing pressure, providing basic information for demographic models [8,9,10]. Among the most important parameters for this purpose are the ones related to the age and growth of the species [11]. The number of age and growth studies in elasmobranchs has increased significantly in recent years [12]; the techniques and structures used for these purposes have
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