To better manage fish stocks, fisheries scientists use various data, including age and growth, to inform stock assessments and provide management advice. However, many non-targeted species, important to the marine ecosystem, including Pseudocarcharias kamoharai still lack such studies which may impede comprehensive assessment of stock status. This study presents the age, growth, and sexual maturity of this species from the Tropical Eastern Atlantic Ocean by examining vertebral samples and reproductive tracts. All samples were collected by Chinese Tuna Fishery Scientific Observers between November 2012 and May 2020, with sizes ranging from 46 to 101 cm fork length (FL). Four age enhancement techniques applied on whole and sectioned vertebral centra were compared. Four growth models fitted to the age data were also compared and the corrected Akaike information criterion was used to select the most plausible model. Whole vertebral centra stained with alizarin red S solution showed clearer growth band-pairs, and age ranged from 2 to 10 years (females) and from 2 to 11 years (males). No significant differences were observed in growth and age composition by sex in the sample. The three-parameter von Bertalanffy growth function presented the best fit to describe the growth of combined sexes of this species (L∞ = 107.8 cm FL, k = 0.18 year^–1). Male specimens attained age-at-50% maturity (4.55 years) earlier than females (5.91 years). The estimated longevities were 11.95 and 13.33 years for females and males, respectively. The present study provides useful life history information, intending to elucidate the biology of this poorly managed shark species.

Oceanic temperature fluctuations are one of the leading factors affecting marine fish populations. Indian Ocean Dipole (IOD), characterized as the sea surface temperature (SST) anomaly change, is an ocean–atmosphere interactive process causing interannual climate variability in the Indian Ocean. Influences of the IOD on the tuna catch rates are supported by previous research. Yet, there remains limited information about the impacts on the abundance of tuna stocks. In this study, we used the standardized Catch Per Unit Effort (CPUE) index to present the stock abundance and compared the effects of the IOD on the bigeye tuna (Thunnus obesus) and yellowfin tuna (Thunnus albacares) among different management areas of the Indian Ocean Tuna Commission (IOTC). Results show significant correlations between IOD events on both species’ abundance in the tropical western Indian Ocean. However, in the tropical eastern Indian Ocean and the southern Indian Ocean, neither bigeye nor yellowfin tuna abundances were significantly correlated by the IOD. For the whole Indian Ocean, IOD was significantly correlated uniquely with the yellowfin tuna abundance. Our results emphasized the importance of evaluating the climate variability effects over fisheries abundance species by species and per fishing areas analyses.

Sharks occupy an important ecological niche in marine ecosystems. As top predators, they can restrict and control the behavior, numbers and composition of other species through downward effects, and play an essential role in ecosystem stability. Shark fishery data are limited, and for most Chondrichthyes species there is no formal fishery resource assessment at a global level. In this study, we applied the length-based Bayesian biomass (LBB) estimation method to assess the stock status of four common shark bycatch species of which more than 100 samples were collected in coastal waters of the northern South China Sea. Estimates of the length of 50% of individuals captured by gear/the length at first capture that maximized the catch and biomass (L_c/L_{c_opt}) of a species ranged from 0.49 to 1.4; the draughtsboard shark Cephaloscyllium sarawakensis had the highest value, and the shortnose dogfish Squalus brevirostris had the lowest. Estimates of the collected biomass/biomass of the maximum sustainable yield (B/B_MSY) ranged from 0.86 to 1.9. Both C. sarawakensis and the spadenose shark Scoliodon laticaudus were fully exploited, while the spatulasnout catshark Apristurus platyrhynchus and S. brevirostris were in good condition. To verify the stability of the LBB, length frequency data for the most common species S. laticaudus were divided into different size-class intervals; simulations revealed estimated parameters based on these to be insensitive to differences in intervals, except for the smallest (10 mm), which did not affect evaluation results. These results can be used to provide a scientific basis on which shark fisheries in this region can be managed and prior parameters for related resource assessment methods can be determined.

Age and growth parameters were estimated for the yellowfin tuna Thunnus albacares (Bonnaterre, 1788). Atotal of 443 individuals were sampled from China longline fisheries in the eastern and central Pacific Ocean from February to November 2006. The von Bertalanffy growth parameters were estimated at L∞ = 175.9 cm fork length, k = 0.52 year-1, and t0 = 0.19 year. The total mortality rate (Z) was estimated to be from 1.19 to 1.93 year-1, the fishing mortality (F) and the natural mortality (M) were calculated to be 0.91 year-1 and 0.65 year-1, respectively. The rate of exploitation (U) was estimated to be 0.46. This study provides estimates of growth and mortality rate for yellowfin tuna in the eastern and central Pacific Ocean, which may be used as biological input parameters in future stock assessments for the oceanic region. However, age analysis with other techniques, additional validation of the size composition and stock structure are also needed