Preliminary Assessment of the Stock Status of Atlantic Bonito ( Sarda sarda ) in the Northeastern Part of the Atlantic O
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iminary Assessment of the Stock Status of Atlantic Bonito (Sarda sarda) in the Northeastern Part of the Atlantic Ocean N. G. Petukhova* Russian Research Institute of Fisheries and Oceanography, Moscow, Russia *e-mail: [email protected] Received February 10, 2020; revised March 10, 2020; accepted March 24, 2020
Abstract—Based on the Russian fishery-biological data, an attempt was made to assess the stock status of Atlantic bonito Sarda sarda in the northeastern part of the Atlantic Ocean using the length-based spawning potential ratio (LBSPR) method. Values of the parameters of the Bertalanffy equation are calculated for Atlantic bonito: the theoretical maximum length of an individual is 75.6 cm and growth coefficient is 0.41. The values of the length where 50 and 95% of the fish are mature are 44.7 and 57.0 cm, respectively. The resulting estimate of the spawning potential ratio (0.28) is lower than the biological target reference point (0.40) and formally indicates an overfishing status of the stock. Keywords: Atlantic bonito Sarda sarda, life history parameters, stock assessment, by-catch, LBSPR, SPR DOI: 10.1134/S0032945220050069
The proportion of Atlantic bonito Sarda sarda is the largest among other representatives of the group of small tunas1 in world catches (Fig. 1). The species is an object of industrial and artisanal fisheries in coastal states (Bulatov et al., 2019). There is no Russian specialized fishery for Atlantic bonito, although this species is caught as by-catch during the trawling of small pelagic fish species (Cunene horse mackerel Trachurus trecae, Atlantic chub mackerel Scomber colias, round sardinella Sardinella aurita, etc.) mainly in waters of Morocco, Mauritania, and Senegal (Nesterov et al., 2017). The Russian by-catch of bonito varies from 16 t in 2004 to 2293 t in 2011 (Fig. 2). The ICCAT does not currently regulate fishery for Atlantic bonito along with other representatives of the group of small tunas; however, it does not rule out the member countries of the Commission to regulate the exploitation of its stocks in the area of their jurisdiction. This is determined by certain difficulties concerning the assessment of the stock status due to incomplete official fishery statistics and insufficient biological studies. Since the ICCAT database has information gaps, the available information support for Atlantic bonito in the northeastern Atlantic Ocean does not allow the use of traditional models of the abundance dynamics to assess its stock status. The ICCAT Small Tunas Species Group collects and generalizes the estimates of the parameters of the 1 According
to the classification of the International Commission for the Conservation of Atlantic Tunas (ICCAT), Atlantic bonito is included in the group of “small tunas”, although this species is not taxonomically related to tunas (ICCAT, 2019).
life history of small tunas according to the results of studies of the member countries of the Commission and assesses the stock of their separate species. Since Atlantic bonito is included in th
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