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Stock assessment for Atlantic yellowfin tuna based on extended surplus production model considering life history
Zhipan Tian, Fei Wang, Siquan Tian, Qiuyun Ma
2022, 41(8): 41-51. doi: 10.1007/s13131-021-1924-x  Published:2022-08-15
Keywords: population dynamics, selectivity, tropical tuna, fishery management
The modern fishery stock assessment could be conducted by various models, such as Stock Synthesis model with high data requirement and complicated model structure, and the basic surplus production model, which fails to incorporate individual growth, maturity, and fishery selectivity, etc. In this study, the Just Another Bayesian Biomass Assessment (JABBA) Select which is relatively balanced between complex and simple models, was used to conduct stock assessment for yellowfin tuna (Thunnus albacares) in the Atlantic Ocean. Its population dynamics was evaluated, considering the influence of selectivity patterns and different catch per unit effort (CPUE) indices on the stock assessment results. The model with three joint longline standardized CPUE indices and logistic selectivity pattern performed well, without significant retrospective pattern. The results indicated that the stock is not overfished and not subject to overfishing in 2018. Sensitivity analyses indicated that stock assessment results are robust to natural mortality but sensitive to steepness of the stock-recruitment relationship and fishing selectivity. High steepness was revealed to be more appropriate for this stock, while the fishing selectivity has greater influence to the assessment results than life history parameters. Overall, JABBA-Select is suitable for the stock assessment of Atlantic yellowfin tuna with different selectivity patterns, and the assumptions of natural mortality and selectivity pattern should be improved to reduce uncertainties.
Assessment of the Tessier and BCR sequential extraction procedures for elemental partitioning of Ca, Fe, Mn, Al, and Ti and their application to surface sediments from Chinese continental shelf
LIU Yanli, ZHANG Jing, HE Huijun
2018, 37(5): 22-28. doi: 10.1007/s13131-018-1189-1
Keywords: elemental fractionation, surface sediments, Tessier SEP, BCR SEP, efficiency, selectivity
Surface sediments can integrate a wide variety of information of seawater in marginal seas, e.g., the Quaternary sedimentary shelf such as the East China Sea (ECS) and Yellow Sea (YS). The Tessier and BCR sequential extraction procedures (SEPs) have been widely applied for extraction of various geochemical phases from sediments. To choose a suitable SEP for phase extraction of sediments from the above Quaternary sedimentary shelf, efficiency and selectivity experiments were conducted on typical individual minerals and the applicability of each SEP was assessed for natural sediments (the natural sediment standard GSD-9 and three surface sediment samples). The geochemical represented elements (Ca, Fe, Mn, Al, and Ti) were measured using both SEPs. Both SEPs have good dissolution efficiency and selectivity for the targeted geochemical phases; the optimized extractant volume for each fraction was determined. The Tessier SEP is particularly recommended for the study of adsorption-desorption process. The application of the Tessier SEP to surface sediments can furnish valuable information, including the productivity conditions (via the reducible fraction Mn) and sedimentary environments (via the carbonate fraction Ca). These results confirm that the Tessier SEP is suitable for elemental fractionation in sediments from the Chinese continental shelf.
A NEW METHOD FOR SEPARATION AND DETERMINATION OF U AND Th IN DEEP-SEA MANGANESE NODULES
LUO SHANGDE, SHI WENYUAN, CHEN ZHEN, HUANG YIPU
1987(1): 87-93.
A new and simple method for separation and determination of U and Th in manganese nodules has been developed.The results show that the addition of NH4NO3 to the dilute HNO3 medium increases the selectivity of anion-exchange separation of U and Th.The simple procedure and high recoveries of the method make it valuable to the analyses of U and Th in manganese nodules.
Evaluation of the performance of alternative assessment configurations to account for the spatial heterogeneity in age-structure: a simulation study based on Indian Ocean albacore tuna
Guan Wenjiang, Wu Jiawen, Tian Siquan
2019, 38(10): 9-19. doi: 10.1007/s13131-019-1485-4
Keywords: spatial structure|simulation|stock assessment|Indian Ocean|Thunnus alalunga
Various population structures or spatial heterogeneities in population distribution have been an important source of model misspecification and have had an impact on estimation performance in fisheries stock assessment. In this study, we simulated the Indian Ocean albacore spatial heterogeneity in age-structure using Stock Synthesis according to the stage-dependent migration rate and region-dependent fishing mortality rate and generated the stock assessment data. Based on these data, we investigated the performances of different spatial configurations, selectivity curves and selections of CPUE(catch per unit effort) indices of the assessment models which were used to account for spatial heterogeneity. The results showed:(1) although the spatially explicit configurations, which exactly matched the operating model, provided unbiased and accurate estimates of relative spawning biomass, relative fishing mortality rate and maximum sustainable yield in all simulation scenarios, their performance may be very poor if there were mismatches between them and the operating model due to gaps in knowledge and data; (2) for spatially explicit assessment configuration, the correct boundary was required, but for non-spatially explicit assessment configuration, it seemed more important for analysts to partition the area to properly reflect the transition in field data and to effectively account for the impacts of ignoring the spatial structure by using the additional spatially referenced parameters; (3) although the areas-as-fleets methods and flexible time-varying selectivity curves could be used as better alternative approaches to account for spatial structure, these configurations could not completely eliminate the impacts of model misspecification and the quality of estimates of different quantities from the same assessment model may be inconsistent or the performance of the same assessment configuration may fluctuate significantly between simulation scenarios; (4) although the worst estimates could generally be avoided by using multiple CPUE indices, there were no best solutions to select or regenerate the CPUE indices to account for the impacts of the ignored spatial structure to obviously improve the quality of stock assessment. Compared with the results of assessment model configurations which are used to account for the spatial structure by different modelers, the performances of the configurations are always case-specific except for spatially explicit configurations which exactly match the operating model. In this sense, our study will not only provide some insights into the current Indian Ocean albacore stock assessment but also enrich existing knowledge regarding the performance of assessment configurations to account for spatial structure.
Effect of UV-B radiation on the feeding behavior of the rotifer Brachionus plicatilis
FENG Lei, LI Xin, WANG Jinhe, HAN Honglei, TANG Xuexi, CHEN Xiguang
2007(4): 82-92.
Keywords: UV-B radiation, feeding, microalgae, rotifer, Brachionus plicatilis
Effect of UV-B radiation on the feeding behaviour of marine zooplankton is important to assessing the health harm of marine ecosystem due to the gradually enhanced UV-B radiation in air. However, there are a few studies on this topic. The feeding behavior of the rotifer, Brachionus plicatilis, under the treatment of UV-B radiation on five species of microalgae, i.e., Chlorella sp., Tetraselmis chuii, Isochrysis galbana Park 8701, Chaetoceros muelleri Lermumerman, and Nitzschia clostertum, was studied. The results showed that the filtering and feeding rates of the rotifer decreased significantly with the dose increase of UV-B radiation when fed with five species of microalgae respectively (P<0.05) which indicates UV-B radiation inhibits the feeding activities of the rotifer on microalage. The mixed culture experiments shows the rotifer preferred to feed Chlorella sp., then C. muelleri,I. galbana, N. clostertum and T. chuii in turn if without UV-B radiation. Under the highest dose of UV-B radiation treatment (2.70 kJ/m2), the rotifer preferred to feed C. muelleri, then Chlorella sp., N. clostertum, I. galbana and T. chuii in turn. Chlorella sp., I. galbana and C. muelleri became the more favorite foods of the rotifer while T. chuii and N. clostertum became less favorite foods. The change of feeding rate and feeding selectivity of zooplankton driven by the enhanced UV-B radiation will lead to the change in the structure of phytoplankton community.