Using LBB Tools to Assess Miter Squid Stock in the Northeastern South China Sea

Abstract

Based on length frequency data of miter squid (Uroteuthis chinensis) collected in the northeastern South China Sea in 1975–1977, 1997–1999, and 2018–2019, asymptotic length, optimal length at first capture, relative mortality, and relative biomass of the stock were estimated using length-based Bayesian biomass estimation (LBB). The LBB-estimated asymptotic length for 2018–2019 was smaller. Optimal lengths at first capture for the later far exceeded average lengths in catches because of a major increase in fishing intensity. Between 1975 and 1977, relative total mortality (Z/K) was low, but it increased in the latter two periods, while relative natural mortality (M/K) showed a downward trend. Relative biomasses (B/B0 and B/Bmsy) indicated that the stock was close to unexploited between 1975 and 1977, but they declined to the levels of 6% and 4% in the later periods, which correspond to growth in fishing horsepower. Indeed, by 2018, fishing horsepower increased by nearly four times the optimal level. The analysis suggests that the stock of miter squid has been overfished since the mid-1980s and is now under heavy fishing pressure. To recover the stock, it is imperative to reduce fishing intensity and enforce size-at-first-capture regulations.

Stock Assessment of Four Dominant Shark Bycatch Species in Bottom Trawl Fisheries in the Northern South China Sea

“…The LBB method can analyze length frequency data from commercial catches of continuously growing species, such as most commercially exploited fish and invertebrates [36,42].…”

“…This process estimates asymptotic length, length at first capture, relative natural mortality, and relative fishing mortality of a species. The resource statuses of poor-data fish species in China have been previously evaluated using this method [36][37][38]. Thus, we estimated the population parameters of four dominant (bycatch) shark species and assessed their stock status using the LBB method based on length frequency data collected by bottom trawl surveys from 2019 to 2021 in the NSCS.…”

Evaluating the stock status of 10 croaker species landed along the north-eastern Arabian Sea using the length-based Bayesian biomass approach

“…However, the former method needs parameters of the maturity ogive (L m50 and L m95 ) as an input besides LF data. Owing to minimal and simple data requirements, LBB has emerged as a powerful tool for stock status estimation of tropical data-deficient fisheries (e.g., Zhang et al, 2020;Barman et al, 2021;Wang et al, 2021;Raza et al, 2022). In the present study, we opted for the LBB, as reliable estimates for the parameters of the maturity curve were not available for all the species.…”