Defense Date


Document Type


Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

David Kerstetter, Ph.D

Second Advisor

Tracey Sutton, Ph.D

Third Advisor

Walter Golet, Ph.D


mesopelagic, bycatch, von Bertalanffy, growth models, length-frequency analysis, otoliths


Escolar, Lepidocybium flavobrunnuem (Smith, 1849), Oilfish, Ruvettus pretiosus (Cocco, 1829), and Snake Mackerel, Gempylus serpens (Cuvier, 1829) belong to the family Gempylidae and are bycatch of the tuna-targeting pelagic longline fishery. There is limited know life-history information on these mesopelagic fishes, especially regarding growth rates. Age estimates were assigned by counting pairs of increment bands formed on the sagittal otoliths of Escolar (n = 133), Oilfish (n = 49), and Snake Mackerel (n = 46) collected between 2007 and 2022. Marginal increment analyses were used to validate age estimates and periodicity of increment formation, but no significant trends were observed and annual band deposition could not be confirmed. Length-frequency analyses were performed on NOAA pelagic observer catch data ranging from 1992-2020 and predicted theoretical maximum size (), growth coefficient (k), time of hatching (tanchor), and age bins. Five growth functions were modeled using maximum likelihood (ML) and nonlinear least-squares (NLS) techniques. The Akaike’s information criteria (AICc) indicated that the Logistic growth function was the best fit for fork length-at-age data for Escolar, the modified VBGF (ML) and 2-parameter VBGF (NLS) were the best fit for fork length-at-age data for Oilfish, and the 2-parameter VBGF was the best fit for fork length-at-age data for Snake Mackerel. Ultimately, sample size and gear selectivity limited this study, estimating parameters outside expected ranges and leading to issues in those predicted models. The data collected in this study is a starting point in understanding growth rates of these valuable non-target fishes.