Changes in population structure and growth of Skipjack tuna, Katsuwonus pelamis, during 30 years of exploitation in the SW Atlantic

Jorge Pablo Castello


DOI: https://doi.org/10.3856/vol42-issue3-fulltext-13

Abstract


The skipjack tuna is the principal tuna species caught in Brazil (with pole and live-bait). Samples taken during the 80`s and the 2004-2009 period provided length, weight and age data. A comparison of the population structure and growth rate was made showing a decrease in the median and means of fork lengths between the 80`s (55 cm) and recent ones (51 cm), an increased participation of smaller individuals (40 cm) in recent catches, a high variability of lengths in each year class and the diminution on the condition factor K. These results indicate that an alteration in this population structure and dynamics may be occurring. The von Bertalanffy growth parameters calculated for the recent years were L∞ = 925 mm; k = 0.16 year-1; to = -2.9. CPUE data for the studied period seems to be stable (mean annual catch of 20thousand tons). However, the used unit of effort in Brazil (fishing days) does not reflect properly the changes in fishing power and technology occurred during 30 years of exploitation. It is concluded that the present situation requires a close monitoring of the stock conditions.


Castello J. Changes in population structure and growth of Skipjack tuna, Katsuwonus pelamis, during 30 years of exploitation in the SW Atlantic. Lat. Am. J. Aquat. Res.. 2017;42(3). Available from: doi:10.3856/vol42-issue3-fulltext-13 [Accessed 24 Jan. 2019].
Castello, J. (2017). Changes in population structure and growth of Skipjack tuna, Katsuwonus pelamis, during 30 years of exploitation in the SW Atlantic. Latin American Journal of Aquatic Research, 42(3). doi:http://dx.doi.org/10.3856/vol42-issue3-fulltext-13