Xiujuan Shan

Tissue-specific accumulation of cadmium and its effects on antioxidative responses in Japanese flounder juveniles

This study investigated the accumulation of cadmium (0-8 mg Cd L⁻¹) and its toxicological effects on oxidative stress biomarkers in different tissues of Japanese flounder juveniles. Following Cd exposure for 28 d, accumulation of Cd in fish was dose-dependent and tissue-specific, with the greatest accumulation in the liver, followed by the kidney, gill, and muscle. Although the gill and liver mounted active antioxidant responses at ≥ 4 mg L⁻¹ Cd including a decrease in glutathione level and GST and GPx activities, the antioxidant response failed to prevent lipid peroxidation induction in these organs. In the kidney, increased GPx and GST activities and decreased SOD activity were observed in fish exposed to high Cd concentrations, but LPO levels did not significantly differ among the exposure concentrations. The gill was most sensitive to oxidative damage, followed by the liver; the kidney was the least affected tissue.

Cadmium toxicity to embryonic-larval development and survival in red sea bream Pagrus major.

At 18 degrees C and 33 psu, 24 and 48 h LC(50) values of cadmium (Cd) for red sea bream Pagrus major embryos were 9.8 and 6.6 mgl(-1), respectively, while 24, 48, 72, and 96 h LC(50) values for larvae were 18.9, 16.2, 8.0, and 5.6 mgl(-1), respectively, indicating that embryos were more sensitive to Cd toxicity than larvae. Cd concentrations at > or =0.8 mgl(-1) led to low hatchability (0-90% in > or =0.8 mgl(-1) solutions vs. 97-100% in lower ones), delay in time to hatch, high mortality (38-100% vs. 1-10%), morphological abnormality (42-100% vs. 1-10%), reduced length (3.55-3.60 vs. 3.71-3.72 mm) in the embryos and larvae. They were Cd concentration dependent and potential biological significant endpoints for assessing the risk of Cd to aquatic organisms. Heart beat and yolk absorption of the larvae were significantly inhibited at some high concentrations but they were not as sensitive as other endpoints to Cd exposure.

Long-Term Changes in Fish Assemblage Structure in the Yellow River Estuary Ecosystem, China

Abstract The Yellow River estuary ecosystem is an important spawning ground for many species found in the Bohai Sea and Yellow Sea and contributes substantially to the fishery resource structure and biological reproduction in the northern China Sea. Based on long-term ecosystem surveys in the Yellow River estuary during the main spawning period (May) of most fishery species from 1959 to 2011, the responses of the ecosystem, including regime shifts in species composition, biomass, diversity, and other related factors, were analyzed in this study. Since the 1980s, the dominant large-size species of high economic value (e.g., Largehead Hairtail Trichiurus lepturus) have been replaced by short-lived, low-trophic-level, planktivorous pelagic species (e.g., Scaly Hairfin Anchovy Setipinna taty and Japanese Anchovy Engraulis japonicus). Currently, traditional commercially targeted fishes, such as the Largehead Hairtail, Red Seabream Pagrus major, and Pacific Herring Clupea pallasii, are locally extinct. There has been a rapid shift of dominant species from highly valued, high-trophic-level, large-sized demersal species with complicated age structures to low-value, low-trophic-level, small-sized pelagic species with simple age structures; this shift has resulted in major changes to the ecological cycle and restoration of fishery resources. The fish catch declined from 421.66 kg/h in 1959 to 0.25 kg/h in 2008 and then increased to 3.62 kg/h in 2011. Diversity and evenness indices showed a continuously increasing trend during 1959–2011. The Yellow River estuary may be significantly compromised by overfishing, climate change, dam construction, and pollution, resulting in the decline of traditional fishing industries and reduced biodiversity in this ecosystem.

Application of otolith shape analysis for stock discrimination and species identification of five goby species (Perciformes: Gobiidae) in the northern Chinese coastal waters

We tested the use of otolith shape analysis to discriminate between species and stocks of five goby species (Ctenotrypauchen chinensis, Odontamblyopus lacepedii, Amblychaeturichthys hexanema, Chaeturichthys stigmatias, and Acanthogobius hasta) found in northern Chinese coastal waters. The five species were well differentiated with high overall classification success using shape indices (83.7%), elliptic Fourier coefficients (98.6%), or the combination of both methods (94.9%). However, shape analysis alone was only moderately successful at discriminating among the four stocks (Liaodong Bay, LD; Bohai Bay, BH; Huanghe (Yellow) River estuary HRE, and Jiaozhou Bay, JZ stocks) of A. hasta (50%–54%) and C. stigmatias (65.7%–75.8%). For these two species, shape analysis was moderately successful at discriminating the HRE or JZ stocks from other stocks, but failed to effectively identify the LD and BH stocks. A large number of otoliths were misclassified between the HRE and JZ stocks, which are geographically well separated. The classification success for stock discrimination was higher using elliptic Fourier coefficients alone (70.2%) or in combination with shape indices (75.8%) than using only shape indices (65.7%) in C. stigmatias whereas there was little difference among the three methods for A. hasta. Our results supported the common belief that otolith shape analysis is generally more effective for interspecific identification than intraspecific discrimination. Moreover, compared with shape indices analysis, Fourier analysis improves classification success during inter- and intra-species discrimination by otolith shape analysis, although this did not necessarily always occur in all fish species.

Size-dependent predation of fish larvae by jellyfish: an experimental evaluation exemplified with the flounder Paralichthys olivaceus larvae and the moon jellyfish Aurelia aurita medusae

This study evaluates the size-dependent predation of fish larvae by jellyfish, exemplified with flounder Paralichthys olivaceus and moon jellyfish Aurelia aurita under laboratory conditions. The effects of some environmental factors on the size-dependent predation were also investigated. The results indicate that the predation rate increased with larval development, until the larvae had developed the ability to actively avoid predation at approximately 11-day post-hatching and decreased thereafter. This suggests a size-dependent predation on the fish larvae. Water temperature and predator size significantly affected the predation rate of the medusae on the fish larvae, but the temperature and size effects were markedly reduced as the larvae reached post-larval stage. These findings suggest that water temperature and jellyfish size interacted with the ontogenetic development of the fish larvae to affect the predation rates. The presence of alternative prey Artemia salina, could alleviate the predation rate on the fish larvae, whereas light conditions showed no effects on the predation rate. Due to their overlaps in spatial and temporal distributions along the north Chinese coast, jellyfish are likely to prey upon flounder larvae and thus affect the recruitment of the wild fish populations.

A comparative study of spatial interpolation methods for determining fishery resources density in the Yellow Sea

Spatial interpolation is a common tool used in the study of fishery ecology, especially for the construction of ecosystem models. To develop an appropriate interpolation method of determining fishery resources density in the Yellow Sea, we tested four frequently used methods, including inverse distance weighted interpolation (IDW), global polynomial interpolation (GPI), local polynomial interpolation (LPI) and ordinary kriging (OK). A cross-validation diagnostic was used to analyze the efficacy of interpolation, and a visual examination was conducted to evaluate the spatial performance of the different methods. The results showed that the original data were not normally distributed. A log transformation was then used to make the data fit a normal distribution. During four survey periods, an exponential model was shown to be the best semivariogram model in August and October 2014, while data from January and May 2015 exhibited the pure nugget effect. Using a paired-samples t test, no significant differences (P>0.05) between predicted and observed data were found in all four of the interpolation methods during the four survey periods. Results of the cross-validation diagnostic demonstrated that OK performed the best in August 2014, while IDW performed better during the other three survey periods. The GPI and LPI methods had relatively poor interpolation results compared to IDW and OK. With respect to the spatial distribution, OK was balanced and was not as disconnected as IDW nor as overly smooth as GPI and LPI, although OK still produced a few “bull’s-eye” patterns in some areas. However, the degree of autocorrelation sometimes limits the application of OK. Thus, OK is highly recommended if data are spatially autocorrelated. With respect to feasibility and accuracy, we recommend IDW to be used as a routine interpolation method. IDW is more accurate than GPI and LPI and has a combination of desirable properties, such as easy accessibility and rapid processing.

Deposition of duststorm particles during 2000–2012 in the South Yellow Sea, China based on satellite data

In this study, about 220 satellite images between 2000 and 2012 were obtained from FY-series, MODIS, CBERS, HJ-1A and HJ-1B to estimate the impact of duststorms on the South Yellow Sea (SYS), which serve as an important source of particles there. The analyzing results from the images support a total occurrence of 88 duststorms (including the locally-generated dusty weather) that affected the SYS during 2000–2012. The annual occurrence was about 4–10 times (10 times in 2000 and 2004; four times in 2009 and 2012), predominantly in March (29%), April (33%) and May (22%). By mapping the distribution of their frequency, the duststorms influencing the SYS were found primarily moving from the northwest (39 times, 44.3%) and west (37 times, 42%) to the study region with only 11 duststorms (12.5%) coming from the north and 1 duststorm (1%) from the southwest. We estimated that an annual amount of 0.5–3.5 million tons of sediment particles was brought to the SYS by the duststorms during 2000–2012.

Changes in fish diversity and community structure in the central and southern Yellow Sea from 2003 to 2015

The central and southern Yellow Sea is an important overwintering ground for many fish species in the Bohai Sea and Yellow Sea. For better understanding the status of the fish community after years of heavy exploitation, variations in fish community structure and diversity were analyzed using data from bottom trawls during 2003–2015. Five fish assemblage indices all showed fluctuations without clear trends from 2003 to 2015, yet there were strong positive and significant correlations ( P < 0.05) among them. The top-five dominant species accounted for a high weight percentage (49.7%–82.1%) in the annual fish catch. Multivariate analysis showed that two year groups could be pooled for the fish community: Group I consisted of the years 2006, 2007, 2008 and 2015, while Group II consisted of the years 2003, 2004, 2005, 2009, 2010 and 2014; the groups aggregated with 63.71% similarity, indicating a high level of similarity among all years. The multivariate dispersion values were 1.455 and 0.818 for Groups I and II, respectively, indicating greater variances in fish assemblage structure in Group I than that in Group II. Similarity of percentage analysis demonstrated that the average similarities for Group I and Group II were 71.58% and 67.51%, respectively. Size-spectra analysis revealed no consistent trend in the intercept and slope ( P > 0.05); there were also no significant differences between the slope of the size-spectra and fishing effort. The catch per unit effort and mean individual weight analyses of the whole fish assemblage both showed a significantly decreasing trend over time. Overall, the results showed that the fish community structure in the central and southern Yellow Sea was relatively stable from 2003 to 2015 and the study could be used as a reference for supporting ecosystem-based fishery management.

Biological responses of small yellow croaker ( Larimichthys polyactis ) to multiple stressors: a case study in the Yellow Sea, China

Temporal changes in biological characteristics of small yellow croaker Larimichthys polyactis in the Yellow Sea were examined for the period of 1960–2008. The body size and age of small yellow croaker decreased substantially, in particular, average length of fish in 2008 was reduced by ~85% than those occurring in 1985, and at that time ~93% of the total catch was dominated by one-year-old individuals. Correspondingly, growth parameters also varied significantly over the years, i.e., k (growth coefficient) and t0 (zero-length age) gradually increased from 0.26 and–0.58 year in 1960 to 0.56 and–0.25 year in 2008, respectively. Although, L∞ (body length) sharply decreased from 34.21 cm in 1960 to 24.06 cm in 2008, and tr (inflexion age) decreased from 3.78 year in 1960 to 1.61 year in 2008. There was a great increase both in natural mortality coefficient and fishing mortality coefficient. However, according to the gray correlation analysis, changes in the biological characteristics of small yellow croaker were induced by different stressors ranked as: fishing vessel power>feeding grade>sea surface temperature. This study suggests that the active fishery management measures for biological characters of fish populations should be considered.

Population Dynamics of Fish Species in a Marine Ecosystem: A Case Study in the Bohai Sea, China

Abstract There were rapid shifts of the dominant species in the Bohai Sea from the 1950s to the 1990s, with large-sized, high-valued species (e.g., Small Yellow Croaker Larimichthys polyactis and Largehead Hairtail Trichiurus lepturus) being replaced by small-sized, low-valued species (e.g., Japanese Anchovy Engraulis japonicus and Hairfin Anchovy Setipinna taty). From the 1990s to the present, the Small Yellow Croaker and some of the small-sized species (Hairfin Anchovy and Dotted Gizzard Shad Konosirus punctatus) have become the dominant species. The food web is now simple, with species from relatively low trophic levels controlling the energy flow within the fishery ecosystem. Along with the shift in community structure, the abundance of dominant species changed, the diversity of fish species and species number density decreased, and interannual and seasonal variations in species number density were found. Fish abundance had a decreasing trend and fish interannual and seasonal distribution greatly changed. Variation in the sizes of the ecological niches of the dominant species regulated the succession of the fish community, and the alteration of ecological niches caused changes in the fishery community.