Patagonotothen ramsayi

Abstract

This species has a relatively small range on the continental shelf and slope of the southern part of the Patagonia Sea where it plays an important ecological role as a prey item for larger marine species. The majority of its global population is concentrated in southern Argentina, including the Malvinas Islands, where the main fishing ground is located. One generation length is estimated as 10 years. It is relatively slow-growing and late to maturity with relatively low fecundity, which may cause it to be susceptible to declines when facing heavy fishing pressure. Previous to 2006, it was mostly discarded as bycatch in large quantities beginning in the 1980s. A large-scale, commercial fishery began in 2007 in the Malvinas area. In areas outside the Malvinas closer to the Argentine mainland, it is taken in fisheries in relatively small amounts. According to stock assessment models based on catch per unit effort data and fishery independent trawl surveys, the estimated biomass for the period of 2005 to 2018 was highest in 2005 and then declined by 79% to a low in 2018. According to the 2019 and 2020 survey results, biomass has continued to decline. Biomass trends prior to 2005 are poorly understood, but based on these data, it is suspected that its population has declined by 40-50% on a global-level over the past one and a half generation lengths, or 15 years. In addition, declines in length at maturity and average length of individuals in the survey catch have also occurred. The cause of decline is poorly understood, but may be attributed in part to fishing activity or a shift in the spatial distribution of its abundance to areas adjacent to the Malvinas. Several fishery management measures are in place, catches have been at a relatively low level and it is not considered overfished. Due to the uncertainty associated with the cause of decline and lack of data prior to 2005, it is not possible to estimate the population trend to cover a three generation length period (either in the past or into the future) at this time. It is listed as Data Deficient with a strong recommendation to conduct studies to improve the understanding of this decline both within the Malvinas area and areas adjacent to it.