Species Composition and Protection of Fish Eggs and Larvae in Spawning Ground of Liaodong Bay

[Objective] The paper was to explore the species composition, number distribution and seasonal dynamics of fish eggs and larvae in Liaodong Bay in 2008. The protection and exploitation status of spawning ground in Liaodong Bay was analyzed, and the corresponding protection measures were put forward. [Methods] The species composition of fish eggs and larvae in spawning ground of Liaodong Bay was investigated by horizontal trawling associated with vertical trawling with zooplankton net in May, July, September and October in 2008. [Result] It was found that 7 724 eggs and 229 larvae of fishes belonging to 32 taxa were collected, in which 29 taxa were identified as species, belonging to 9 genera, 21 families and 28 orders, 2 taxa were identified to only family level, and one failed to be identified. The main spawning groups were Cynoglossus joyneri, Engraulis japonicus, Johnius belengerii, Larimichthys polyactis, Konosirus punctatus, Sardinella zunasi, and Scomberomorus niphonius, and the main spawning ground was found in northern waters and Changxing Island waters in Liaodao Bay. There was slightly less spawning species in 2008 compared with 1998, especially the number of fish eggs and larvae decreased greatly. [Conclusion] The effective measures for protection of spawning grounds in Liaodong Bay are suggested, including control of fishing intensity, development of artificial reefs, establishment of germplasm resources reserves, and standardization of compensation standards for marine ecological damage.

Larva fish assemblage structure in three-dimensional floating wetlands and non-floating wetlands in the Changjiang River estuary

Fish populations have declined in many estuarine and freshwater ecosystems in part due to the loss of habitat in recent decades.Reconstructing lost habitat for larvae fish is a potential method for recovering larvae fish populations.Three-dimensional artificial floating wetlands(AFWs)on which Phragmites australis was planted were experimentally deployed to recover the lost habitat in the Changjiang(Yangtze)River estuary from May to July 2018.The AFW area was characterized by slow velocity,high transparency,low dissolved oxygen,and relatively constant water temperature.The total individuals of larvae fish in the AFW area(12122 in total)was higher than that in the non-AFW area(1250 in total),and the densities of most larvae fish species were higher in the AFW habitat than in the non-AFW area.The distributions of larvae fish species were positively influenced by habitat type because they were strongly related to the negative part of the first axis of the redundancy analysis,and Cyprinus carpio and Cyprinus auratus were inclined to habitat in the slow velocity and high transparency AFW habitat area.These results indicate that larvae fish species are inclined to inhabit the AFW habitat.The use of three-dimensional P.australis AFWs would be a potential method for enhancing the habitat of larvae fish in the degraded habitats along the estuary.

Composition and ecological distribution of ichthyoplankton in eastern Beibu Gulf

Surveys were conducted in four seasons in the eastern Beibu Gulf from July 2006 to November 2007, to determine the ichthyoplankton composition, abundance, as well as environmental factors impacted on their spatiotemporal distributions. The fish eggs and larvae were sorted from 303 zooplankton quantitative samples, in which at least 1 order, 60 families, 31 genera and 61 species of fish eggs and larvae were identified. The species number was highest in summer whereas lowest in winter. With the most abundant fish egg （the average density was 2.41 ind./m3）, spring was the main spawning season, while the greatest mean density of fish larva was 1.35 ind./m3 in summer. In the whole year around, fish eggs had the trends to aggregate in the nearshore of Guangxi coast, fish larvae were more abundant in the northern water. Relationships between fish eggs and larvae abundance and environmental factors were analyzed by using the Yield-Density model. The spatio- temporal distribution of ichthyoplankton in eastern Beibu Gulf was closely related to the Chl a concentration, and the optimal temperature, salinity and Chl a were 19.4-21.7℃, 31.8-33.1 and 1.5-4.8 mg/m3, respectively. Additionally, the distribution of fish larvae could be effected by ocean currents in summer and autumn.

Exploring the potential for an evolutionarily conserved role of the taste 1 receptor gene family in gut sensing mechanisms of fish

In this study,we investigated the transcriptional spatio-temporal dynamics of the taste 1 receptor(T1R)gene family repertoire in seabream(Sparus aurata[sa]),during larval ontogeny and in adult tissues.In early larval development,sa T1R expression arises heterochronously,i.e.the extraoral taste-related perception in the gastrointestinal tract(GIT)anticipates first exogenous feeding(at 9 days post hatching[dph]),followed by the buccal/intraoral perception from 14 dph onwards,supporting the hypothesis that the early onset of the molecular machinery underlying sa T1R expression in the GIT is not induced by food but rather genetically hardwired.During adulthood,we characterized the expression patterns of sa T1R within specific tissues(n=4)distributed in oropharingeal,GIT and brain regions substantiating their functional versatility as chemosensory signaling players to a variety of biological functions beyond oral taste sensation.Further,we provided for the first time direct evidences in fish for m RNA coexpression of a subset of sa T1R genes(mostly sa T1R3,i.e.the common subunit of the heterodimeric T1R complexes for the detection of“sweet”and“umami”substances),with the selected gut peptides ghrelin(ghr),cholecystokinin(cck),hormone peptide yy(pyy)and proglucagon(pg).Each peptide defines the enteroendocrine cells(ECCs)identity,and establishes on morphological basis,a direct link for T1R chemosensing in the regulation of fish digestive processes.Finally,we analyzed the spatial gene expression patterns of 2 taste signaling components functionally homologous to the mammalian G(i)a subunit gustducin,namely sa G(i)a1 and sa G(i)a2,and demonstrated their co-localization with the sa T1R3in EECs,thus validating their direct involvement in taste-like transduction mechanisms of the fish GIT.In conclusion,data provide new insights in the evolutionary conservation of gut sensing in fish suggesting a conserved role for nutrient sensors modulating entero-endocrine secretion.