Temporal changes in lengths of Dolphinfish revealed by sampling at sportfishing tournaments in the southeastern United States

• Published in: North American Journal of Fisheries Management
• Main Authors: Rudershausen, P. J., Buckel, J. A., Gregory, R., Stilson, G. R., Dukes, A. W., Gooding, E. L., Runde, B. J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2024
• Subjects: North Atlantic
• Online Access: http://dx.doi.org/10.1002/nafm.11006; https://afspubs.onlinelibrary.wiley.com/doi/pdf/10.1002/nafm.11006

Abstract Objective Our objective was to use sportfishing tournament data to determine whether sizes of Dolphinfish Coryphaena hippurus have been changing in the western North Atlantic (WNA) over recent decades. Methods We sampled North Carolina, South Carolina, and Florida marine sportfishing tournament landings for Dolphinfish lengths. Linear models were separately fitted to length data for males and females by regressing length against year. A subset of these models (analysis of covariance) considered tournament as a factor. Result An analysis of covariance model with a separate regression slope for each tournament provided the best fit to the data for male and female Dolphinfish. Meaningful temporal declines in the length of males and females were found for four of the five tournaments (no changes in length were observed for the fifth tournament). Median total length declines of 168, 105, 103, and 426 mm were predicted for males, and declines of 354, 133, 131, and 246 mm were predicted for females. Declines in the largest observed sizes of Dolphinfish (97.5% confidence limit) were found for most tournament‐ and sex‐specific combinations of data and could suggest excess fishing mortality on the population. Conclusion Declines in Dolphinfish size in the WNA region could have ramifications for conservation of the population given that these size changes translate into reduced individual fecundity of female Dolphinfish. Causes of the size decline could be fishing effects, environmental effects, or a combination of these. Reductions in individual size may be occurring simultaneously with declines in abundance identified in other recent research using fishery‐dependent data collected in the WNA.