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

Abstract

; to = -3.8. CPUE data for the studied period seems to be stable (mean annual catch of 20,000 ton). However, the unit of effort used in Brazil (fishing days) does not reflect changes in fishing power and technology properly as occurred during 30 years of exploitation. It is concluded that the present situation requires a close monitoring of the fishery. Keywords: Katsuwonus pelamis, skipjack, population structure, weight-length relationship, condition factor, growth, CPUE, southwestern Atlantic. ; to = -3.8. Los datos de CPUE para el periodo estudiado parecen indicar una estabilidad en el stock (20.000 ton de captura media). Sin embargo, la unidad de esfuerzo utilizada en Brasil (días de pesca), no refleja adecuadamente los cambios en tecnología y poder de pesca que ocurrieron durante 30 años de explotación. Se concluye que la situación actual del stock requiere un monitoreo estricto de sus condiciones. Palabras clave: Katsuwonus pelamis, barrilete, estructura de la población, relación longitud-peso, factor de condición, crecimiento, CPUE, Atlántico sudoccidental.

This is what we know: Assessing the stock status of the data-poor skipjack tuna (Katsuwonus pelamis) fishery in the South China Sea

“…However, the estimated L inf in the SCS is the lowest thus-far reported (Table 2). This may be because the predominant size-class of skipjack tuna elsewhere ranges 40-60 cm (Garbin and Castello, 2014;Hare et al, 2021), while those from the SCS are smaller (20-40 cm). Possible explanations for this include density-dependent effects, the influence of environmental factors (e.g., higher water temperature), and fishing-induced evolution (Zhang et al, 2020).…”

Age and growth of skipjack tuna (Katsuwonus pelamis) in the western equatorial Atlantic based on dorsal spines analysis

“…Analyzing catches over a 30-year period of exploitation since the 1980s, Garbin and Castello (2014) found a significant reduction in median size and greater participation of smaller individuals (<40 cm FL) in catches by the Brazilian fleet operating in the southwestern Atlantic. The analyses made with skipjack tuna dorsal spines in the present study revealed individuals up to five years of age, with a concentration of the two-and-three-year-old groups in fishing activities carried out by the fleet from Areia Branca, RN, whereas Garbin and Castello (2014) found a greater occurrence of individuals aged two to five years based on the dorsal spines method and Uchiyama and Struhsaker (1981) found mostly fish between one and three years of age in the catches from Central Pacific, based on otolith daily increments.…”

“…Unfortunately, however, the number of growth studies for the skipjack tuna has decreased despite the increase in catches in all oceans (Murua et al, 2017). Different techniques and structures have been used to develop age and growth studies on the skipjack tuna, such as tagging and recapture (Hallier and Gaertner, 2006;Gaertner et al, 2008), size frequencies (Garbin and Castello, 2014;Soares et al, 2019), dorsal spines (Vilela and Castello, 1991;Andrade et al, 2004), and otoliths (Adams and Kerstetter, 2014).…”

Dinamika Populasi Ikan Cakalang (Katsuwonus Pelamis) Yang Didaratkan Di Pelabuhan Perikanan Samudera (Pps) Cilacap

“…Penelitan lain [13] di Samudera Hindia menunjukan L∞ 920 mmFL dengan K 0,50 dan t0 -0,0012. Pendugaan juga dilakukan di Samudera Atlantik Barat Daya dan menunjukan nilai L∞ sebesar 669 mmFL dengan K 0,24 dan t0 -3,8 [14]. Perbandingan tersebut menunjukan bahwa rata-rata Cakalang mencapai L∞ pada ukuran 600-900 mmFL.…”