[Population resources and fishery management policies of Schizopygopsis younghusbandi in the Yarlung Zangbo River, China.] / é› é²è—å¸ƒæ±Ÿæ‹‰è¨è£¸è£‚å°»é±¼ç§ç¾¤èµ„æºçŠ¶å†µåŠå ¶æ¸”ä¸šç®¡ç†å¯¹ç­–.

Schizopygopsis younghusbandi, an endemic species in China, is threatened by overfi-shing and biological invasion. With 694 individuals collected during August 2008 to August 2009 from the Xietongmen to Nimu of Yarlung Zangbo River, Tibet, the population resources and fishery management policies of the fish were studied using per-recruit models. The total instantaneous annual mortality (Z) of S. younghusbandi was 0.81 year-1 for females and 0.78 year-1 for males. The range of natural mortality (M) of females and males were 0.17-0.27 year-1 and 0.21-0.33 year-1, respectively. The range of current fishing mortality (Fcur) was 0.54-0.64 year-1 for females and 0.45-0.57 year-1 for males. The range of spawning potential ratio of S. younghusbandi was 10.1%-17.9% for females, being significantly lower than the threshold reference point (F25%). That for males was 28.3%-43.6%, with 22.3% of which was higher than the target reference point (F40%). This result indicated that the stock of S. younghusbandi had been over-exploited under the current fishery management policy. To evaluate the protective effects of capture age and seasonal closure, 14 different fishery management policies were simulated. The results showed that the stock of S. younghusbandi would be effectively conserved by enhancing the capture age to not less than 10 years old or setting the seasonal closure from February to June.

[Bioaccumulation and Biomagnification of Heavy Metals in Three Gorges Reservoir and Effect of Biological Factors].

Three Gorges Reservoir (TGR) reached the maximum water level (175 m) of impoundment in Oct. 2010. In order to reveal the potential influence of the greatest water-level impoundment on the heavy metal pollution in the typical waters of TGR, the content level of trace metals ( Hg, Cd and Pb) in biota and potential biomagnification along the aquatic food chain were investigated in the main stem of TGR from July 2011 to August 2012, as well as the relationship between the trace metal concentrations of aquatic consumers (fish and aquatic invertebrate) and biological factors. Our study showed that no individual data of the three trace metals in biota exceeded the edible safety criteria of aquatic products in China and FAO. In contrast with those before the impoundment of TGR, Hg showed a little higher, while Cd and Pb exhibited a little lower level after the impoundment. Trace metals in TGR exhibited relatively lower concentrations compared with those in reservoirs in other countries. Significant correlations were found between the Cd concentration and body size (body length and body weight) of Cyprinus carpio, as well as the Hg concentration and body size (body length and body weight) of Erythroculter ilishaeformis. As for feeding habits, there was statistically significant difference between trace metal concentrations in herbivorous, planktonic, omnivorous and carnivorous fish. However, no significant difference was found between the metal concentrations in fish with different habitats (pelagic, mesopelagic and benthic). Even so, the overall trend was that fish living in benthic layer had higher heavy metal concentrations than those in pelagic and mesopelagic zones. The regression slopes of log-Hg concentration versus delta(15)N, served as an indicator of trophic magnification factor (TMF). Significant correlations (P < 0.05) were observed for Hg in the food web of TGR. TMF of Hg in TGR indicated lower level (0.046-0.066) in contrast with those in the reservoirs of United States and Canada, and this was explained by the relatively lower organic carbon in the soil and sediment of TGR.

Stock assessment and management implications of an endemic fish, Oxygymnocypris stewartii, in the Yarlung Zangbo River in Tibet, China.

BACKGROUND: Oxygymnocypris stewartii is an endemic species only inhabiting the middle and upper reaches of the Yarlung Zangbo River and its tributaries at altitudes above 3600 m in the Qinghai-Tibet Plateau and has suffered a continuous decline of population size owing to anthropogenic disturbance. However, little is known about the stock status of this species and how to protect it. In this study, we evaluated the population status of O. stewartii and investigated two management policies including the minimum age limits and seasonal closure in the Yarlung Zangbo River. RESULTS: Estimates of the total mortality rate were 0.35 year-1 for females and 0.65 year-1 for males. The natural mortality rates were estimated as 0.10 and 0.22 year-1 for females and 0.12 and 0.29 year-1 for males using two empirical methods. The O. stewartii population may be in near full exploitation under the current harvesting strategy in the Yarlung Zangbo River, with a high chance of recruitment failure in the future. Although both minimum age limits and seasonal closure could be effective measures to conserve the O. stewartii stock, it was proposed that aseasonal closure was implemented each year from September to December according to the complexity of the application and the effects on the income of local fishermen and on the biological invasion. CONCLUSIONS: The stock of O. stewartii may bein near full exploitation under the current harvesting strategy, with a high chance of recruitment failure in the future. Our results indicated that the imposition of the seasonal closure from September to December might be the effective measure to conserve the O. stewartii population.

The complete mitogenome sequence of Ptychobarbus dipogon (Cypriniformes: Cyprinidae).

The complete mitochondrial genome of Ptychobarbus dipogon is 16,787 bp in length, consisting of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and 2 non-coding regions: control region (CR) and origin of light-strand replication (OL). The gene order of P. dipogon mitogenome is similar to those observed in most other vertebrates. The complete mitogenome sequence of P. dipogon can provide useful data for further studies on population structure, phylogenetics and conservation genetics of this species.

[Effect of feed residues on the release of nitrogen and phosphorus of pond sediment].

The effect of feed residues on release law of nitrogen and phosphorus in water-sediment interface was studied under the simulated condition in laboratory. Two sets of conditions were applied in this study, static condition (A group) and feed add condition (B group). The results show that DO in A group is higher than that in B group (P < 0.05). The pH value is neutral in A group, but pH value of B group became weak acidic. After adding the feed, nitrate nitrogen concentration in A group is higher than that in B group (P < 0.05), but orthophosphate concentration in A group is lower than that in B group (P < 0.05). At the 2-14th day of experiment, ammonia concentration in A group is higher than that in B group (P < 0.05), but since then the ammonia concentration in B group begins to rise. At the end of the test, ammonia concentration in B group is higher than that in A group (P < 0.05). At the beginning of the experiment, ammonia and nitrate nitrogen release restrained in B group. Nitrogen increases first, and then decreases in A group, but the changing regulation is completely opposite in B group. Feed decomposition can produce a large amount of phosphorus in B group, at the same time, orthophosphate changing regulation increases first and then decreases.

Effects of non-steroidal aromatase inhibitor letrozole on sex inversion and spermatogenesis in yellow catfish Pelteobagrus fulvidraco.

The effects of letrozole (LZ), a potent nonsteroidal aromatase inhibitor (AI), on growth performance, sex inversion, and sex changes were investigated in yellow catfish (Pelteobagrus fulvidraco), which display sexual dimorphic growth. Growth performance was promoted significantly in the low-dose LZ treatment, compared with the control. Four LZ treatments produced dose-dependent male proportions that were significantly higher than that of the control. Histological examination of testes treated by LZ displayed a large amount of spermatozoa and enlarged lobule lumens, indicating that LZ treatments can potentially stimulate spermatogenesis. Changes of sex proportions 45 days after the end of the LZ treatments prove that the female germ cells possess a certain degree of bipotentiality. These results suggest that aromatase activity plays a vital role in sex differentiation, as in other teleosts, with inhibition of aromatase activity by AI bringing about sex inversion.

Blood cells of a sisorid catfish Glyptosternum maculatum (Siluriformes: Sisoridae), in Tibetan Plateau.

The peripheral blood cells of a sisorid catfish Glyptosternum maculatum were studied using light microscope and transmission electron microscope. The size of cells and nucleus, and the percentage of different leucocytes were also described. Erythrocytes and four types of leucocytes: lymphocytes, heterophils, monocytes, and thrombocytes were characterized in G. maculatum blood. The dividing erythrocytes could be found sporadically. A plasma cell was observed under a transmission electron microscope. The morphology and structure of blood cells of G. maculatum were basically similar to those of other fish species, although there were also main differences, such as larger erythrocytes than other catfishes, absence of basophils and acidophils, and various types of thrombocytes (five types: lone nucleus, fusiform, tadpole-like, oval, and in a cluster).