Group items tagged

According to the latest report on the state of World Food and Agriculture Organization fisheries and aquaculture (SOFIA, 2022), skipjack (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) are among the five most caught finfish species of the world, with 2,827 and 1,569 thousand tons in 2020, respectively. The tropical purse seiners deploy large nets around tuna schools in the tropical waters of the world. This method targets three main tuna species, skipjack, yellowfin and bigeye (Thunnus obesus) tunas, which are mainly used for canning or frozen markets. This important fishery provides employment opportunities for many people in developing countries. Landings for the European long-distance fishery targeting tuna and tuna-like fishes from Indian Ocean, amounted to 303,638 tons valued at EUR 423.7 million (Prellezo et al., 2022), where the Spanish fleet of purse seiners targeting tropical tuna is the most important. The Spanish tropical purse seine fleet fishing in the Indian Ocean accounts for 26% of the skipjack and yellowfin tunas caught from Indian Ocean, which represent approximately 3% of worldwide catch for both species.

The values used for natural mortality (M) are very influential in stock assessment models, affecting model outcomes and management advice. Natural mortality is one of the most difficult demographic parameters to estimate, and there is often limited information about the true levels. Here, we summarise the evidence used to estimate natural mortality at age for the four main stocks of yellowfin tuna (Indian, Western and Central Pacific, Eastern Pacific, and Atlantic Oceans), including catch curves, tagging experiments, and maximum observed age. We identify important issues for estimating M such as variation with age linked to size, maturity state or senescence, and highlight information gaps. We describe the history of natural mortality values used in stock assessments by the tuna Regional Fisheries Management Organisations responsible for managing each stock and assess the evidence supporting these values. In June 2021, an online meeting was held by the Center for the Advancement of Population Assessment Methodology (CAPAM), to provide advice and guidance on practices for modelling natural mortality in fishery assessments. Based on approaches presented and discussed at the meeting, we develop a range of yellowfin tuna natural mortality estimates for each stock. We also recommend future research to improve these estimates of natural mortality.

The genus Scomberomorus, with 18 nominal species, sustains a significant heterogeneous fishery throughout its range. The sole molecular systematic study of this genus concerned the species group S. regalis, which contains the new world taxa. The species diversity of Scomberomorus in the northern Indian Ocean has not been studied at the molecular level, often leading to misidentifications...