Abstract
Using readings of 1,214 Pacific thread herring (Opisthonema libertate) otoliths collected at 3 fishing locations off the northwestern coasts of Mexico (Bahía Magdalena, Baja California Sur; Mazatlán, Sinaloa; and Guaymas, Sonora), age was assigned and individual growth parameters, mortality, and exploitation rates were estimated. Up to 5 growth marks were read on otoliths and 6 age groups (0–5) were assigned. Growth marks showed annual periodicity. The age–size data set was supplemented with data of 74 larvae (reared in the laboratory from hatchling to 24 d of age) and data of 96 juveniles (collected from the natural environment, between 48 and 210 d of age). A multi-model approach was used to describe the growth of the Pacific thread herring. Five models were evaluated and their appropriateness was ranked according to the Akaike information criterion. The von Bertalanffy model was the most appropriate model for the 3 fishing areas. Parameter estimates (theoretical maximum length [L∞], growth coefficient [k], and age at zero length [t0]) were L∞ = 18.68, k = 1.13, and t0 = –0.03 for Bahía Magdalena; L∞ = 18.63, k = 1.41, and t0 = –0.02 for Mazatlán; and L∞ = 18.22, k = 1.44, and t0 = –0.002 for Guaymas. The differences between estimators by fishing area were significant (likelihood ratio test). Total mortality (Z), natural mortality (M), and the exploitation rate (E) by fishing area were as follows: M = 0.6, Z = 1.93, and E = 0.7 for Bahía Magdalena; M = 0.6, Z = 1.39, and E = 0.6 for Mazatlán; and M = 0.6, Z = 1.4, and E = 0.6 for Guaymas. Results suggest that the O. libertate population off the northwestern coasts of Mexico does not show signs of overexploitation.
Highlights
M = 0.6, Z = 1.4, and E = 0.6 for Guaymas
Using readings of 1,214 Pacific thread herring (Opisthonema libertate) otoliths collected at 3 fishing locations off the northwestern coasts of Mexico (Bahía Magdalena, Baja California Sur; Mazatlán, Sinaloa; and Guaymas, Sonora), age was assigned and individual growth parameters, mortality, and exploitation rates were estimated
A multi-model approach was used to describe the growth of the Pacific thread herring
Summary
The von Bertalanffy model has been used to describe the growth of marine fish (Katsanevakis and Maravelias 2008), despite the existence of alternative models, because its parameters form the basis for other fisheries analyses, such as yield by recruit (Zhu et al 2009). This type of approach is based on the parsimony principle: from a set of candidate models, the “best” model is selected considering the relationship between model complexity and model adjustment (Aragón-Noriega 2013) This principle aims to evaluate the biological and statistical plausibility of different models for growth description to maximize the potential of data, as opposed to basing this description on only one model (Cailliet et al 2006). The Opisthonema genus comprises 3 thread herring species off northwestern Mexico: Opisthonema libertate, Opisthonema medirastre, and Opisthonema bulleri. These species are distributed from central Baja California, including the Gulf of California, to Ecuador (Whitehead and Rodríguez-Sánchez 1995). The first gill arch (for taxonomic identification) and sagittal otoliths (for age determination) were extracted
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