Genetic variation within and among range-wide populations of three ecotypes of the Japanese grenadier anchovy Coilia nasus with implications to its conservation and management

Studies of range-wide populations can contribute to the comprehension of the relative roles of historical events and contemporary factors that influence genetic variation within and among populations.Japanese grenadier anchovy,Coilia nasus,is a commercially important fish,which widely distributes in the Changjiang River,the coasts of China and Korea,and the Ariake Sea of Japan.This species exhibits three life-history strategies(anadromous,landlocked and freshwater resident forms).Using two fragments of nuclear DNA,genetic variation within and among 18 populations across the rivers and coast of China and Ariake Sea of Japan was examined.Patterns of genetic diversity and divergence among populations varied widely across C.nasus'range,and indicated the different effects of historical events and anthropogenic factors.Strong genetic divergence between freshwater resident populations and other populations suggested that historical geographical factors greatly influenced the genetic structure of C.nasus.Significant genetic differentiation observed among lakes in lower Changjiang River and Huaihe River might be probably influenced by hydraulic facilities.The population genetic structure among the three ecotypes revealed in the present study indicated an important role for environment variation,and the factors responsible for shaping C.nasus different life history strategies might also impact population structure.

Biochemical Factors Affecting the Quality of Products and the Technology of Processing Deep-Sea Fish, the Giant Grenadier Albatrossia pectoralis

The composition of muscle tissues of a deep-sea species, the giant grenadier(Albatrossia pectoralis), and a mesopelagic species, the Alaska pollock(Theragra chalcogramma), are compared. Grenadier is proved to have a higher moisture content(91.7%) and lower protein(7.4%) and lipid(0.3%) contents. The factors responsible for the softening and moisture separation during processing of grenadier are identified. Contents of some fractions of non-protein nitrogenous components, including trimethylamine oxide(TMAO) and free amino acids, are clarified. The proportion of the main myofibrillar proteins myosin and actin, which is considered as an indicator of efficiency of structure formation in fish muscle tissue during processing, is almost 20% lower in giant grenadier than in pollock. The effects of endogenous protease, Са^2+-ATPase and transglutaminase on the processes of autolysis, denaturation, and possibility of myofibrillar proteins cross-linking were also studied. The proposed technology of getting a nutritionally balanced, gel-like, ready-to-use foodstuff from grenadier fillet includes its enrichment with pollock muscle tissue and supplementing with a binary structure-forming agent containing collagen and chitosan. Nutritional value of the products is assessed by the method of biological assay and by determining the denaturation changes of myofibrillar proteins. The modes of fine mincing and thermal processing, as well as the shelf-life of the finished product are justified. The developed technology of producing a ready-to-eat food from giant grenadier will allow a more efficient use of this underutilized resource.

The Signatures of Stable Isotopes δ^(15)N and δ^(13)C in Anadromous and Non-Anadromous Coilia nasus Living in the Yangtze River, and the Adjacent Sea Waters

Stable isotopes are increasingly used to investigate seasonal migrations of aquatic organisms. This study employed stable isotopes (delta C-13 and delta N-15) for Coilia nasus from the lower Yangtze River and the adjacent East China Sea to distinguish different ecotypic groups, ascertain trophic nutrition positions, and reflect environmental influences on C. nasus. delta C-13 signatures of C. nasus sampled from Zhoushan (ZS), Chongming (CM), and Jingjiang (JJ) waters were significantly higher than those from the Poyang Lake (PYL) (P < 0.05). By contrast, delta N-15 signatures of C. nasus in ZS, CM, and JJ groups were significantly lower than those in PYL group (P < 0.05). Basing on delta C-13 and delta N-15 signatures, we could distinguish anadromous (ZS, CM, and JJ) and non-anadromous (PYL) groups. The trophic level (TL) of anadromous C. nasus ranged from 2.90 to 3.04, whereas that of non-anadromous C. nasus was 4.38. C. nasus occupied the middle and top nutrition positions in the marine and Poyang Lake food webs, respectively. C. nasus in Poyang Lake were significantly more enriched in delta N-15 but depleted in delta C-13, suggesting that anthropogenic nutrient inputs and terrigenous organic carbon are important to the Poyang Lake food web. This study is the first to apply delta N-15 and delta C-13 to population assignment studies of C. nasus in the Yangtze River and its affiliated waters. Analysis of stable isotopes (delta N-15 and delta C-13) is shown to be a useful tool for discriminating anadromous and non-anadromous C. nasus.