Total mercury in marine species from the French coast of the Eastern English Channel

Mercury (Hg) in fish can present a potential risk to wildlife and human consumers. Mercury levels were determined in 12 fish species and 2 invertebrate species from the French coast of the Eastern English Channel collected in June and November 2012. Total mercury concentrations in the muscle tissues ranged between 0.04 and 1.63 µg g^-1 (d.w.). Dab and sandeel displayed a significant positive correlation between Hg concentrations and fish length. Seasonal differences in Hg concentrations were observed for dab and shrimp. The lesser weever showed significantly higher concentrations of Hg (0.97 ± 0.34 µg g^-1 d. w.) than all other species. Gobies and sprat, which had the smallest size, showed significantly lower concentrations than herring, whiting, pout and sardine. Among the considered species, flatfish such as dab, flounder, plaice and sole displayed intermediate levels of Hg. In the present study, the fish age expressed as specimen length seems to be one of the major factors governing Hg contents in muscle tissues. Finally, mercury concentrations in commercial fish from the Eastern English Channel were below the levels fixed by the European Union for total mercury in edible parts of fish products.     

Multiscale Spatial and Small-Scale Temporal Variation in the Composition of Riverine Fish Communities

We studied the multiscale (sites, river reaches and rivers) and short-term temporal (monthly) variability in a freshwater fish assemblage. We found that small-scale spatial variation and short-term temporal variability significantly influenced fish community structure in the Macquarie and Namoi Rivers. However, larger scale spatial differences between rivers were the largest source of variation in the data. The interaction between temporal change and spatial variation in fish community structure, whilst statistically significant, was smaller than the variation between rivers. This suggests that although the fish communities within each river changed between sampling occasions, the underlying differences between rivers were maintained. In contrast, the strongest interaction between temporal and spatial effects occurred at the smallest spatial scale, at the level of individual sites. This means whilst the composition of the fish assemblage at a given site may fluctuate, the magnitude of these changes is unlikely to affect larger scale differences between reaches within rivers or between rivers. These results suggest that sampling at any time within a single season will be sufficient to show spatial differences that occur over large spatial scales, such as comparisons between rivers or between biogeographical regions.     

Using Multiple Taxonomic Groups to Index the Ecological Condition of Lakes

Biological indicators of communitiestypically reflect a common environmental signalreflecting the general condition of the ecosystem, as well asindividual signals by indicators differentiallysensitive to particular environmental conditions. Wedescribe here a method of integrating and interpretingsuch indicators from 19 New England lakes for fivetaxonomic groups (diatoms, benthos, zooplankton, fish,and birds). Our approach provides a systematicstandardized way to integrate multiple metrics fromdifferent taxonomic groups by addressing four elementscrucial to analyzing data from multiple indicators: covariate control, re-scaling of data, standardizing the sign of responses, and dimensional reduction. We evaluated the biologicalmetrics against individual environmental stressors andagainst multivariate physicochemical metricscharacterizing general anthropogenic stress among thelakes. The method detected a response to variationin the gross environmental condition of the lakes thatwas correlated across taxa and metrics. In addition,a differential response to near shore conditions wasdemonstrated for fish. The success of the approach inthis study lends support to its general application toecological monitoring involving complex data sets.     

Characterizing Small Subbasins: A Case Study from Coastal Oregon

A fine-grained statisticaly robust probability sample of stream segments is used to compare two small (20,000 hectare) subbasins of the Tillamook watershed, north coastal Oregon. The two subbasins are matched with respect to several variables [size coastal climates], but vary in terms of geology and consequently land use. A total of 67 wadeable + non-wadeable sizes were identified for sampling in the two subbasins (combined) over two field seasons from a sampling universe consisting of the River Reach File 3 (blue lines on 1:100,000 maps). Target variables include an extensive array of physical habitat endpoints, selected water chemistry endpoints, species composition, and relative abundance of both benthic macroinvertebrates and fish. Field protocols generally followed those of the U.S. EPA's Environmental Monitoring and Assessment Program (EMAP).Eleven fish species were encountered, a typically low number for coastal Oregon streams. Exploratory analysis using nonmetric multidimensional scaling revealed that 92.4% of the variation in the fish assemblages could be explained with two ordination axes. Environmental factors related to stream size and substate were the most correlated to these axes. Further, stream segments for the two subbasins tended to map in different areas of species space. Therefore, we also give unweighted probability distributions for several of the factors that heavily on these two axes by subbasins, as well as probability distributions for chemical endpoints. Results from the subset of sites sampled during the first year (21 wadeable sites) reveal: 1) differences between samples from the two subbasins relates to dream size and substrate composition that are consistent with known differences in geology and land use, 2) unexpectedly minor differences between samples from the two subbasins for stream temperature, canopy cover, and dissolved oxygen, 3) differences between samples from the two subbasins for total P, and total N, possibly related to land use, and 4) unexpected differences in samples from the two subbasins for conductivity, probably related to geological factors. Sample size for each subbasin is low and therefore our samples cannot be taken to necessarily characterize either subbasin. However, our findings are consistent with a comprehensive assessment that had been previously produced for one of the two subbasins.All field work was completed in 8 weeks 3-person field crew. We conclude that rapid assessment protocols, based on probability samples at this level of resolution, can be a cost-effective approach to watershed analysis. This approach should be seen as a complement to, rather than a replacement for, systematic surveys that produced finer scale, reach specific information on factors such as channel complexity and cover relevant to in-stream restoration planning.     

水暴露下氟在西伯利亚鲟稚鱼硬骨和软骨中的积累和消除

采用静态水暴露试验方法,设置0.26(对照)、3.1、7.8、18.7、51.8mg·L-1氟离子(F-)5个试验组暴露西伯利亚鲟稚鱼,暴露90d后转移至清水中培养30d,检测了这2个阶段鱼体硬骨和软骨中氟离子含量,探讨了氟离子在西伯利亚鲟稚鱼硬骨和软骨中的积累与消除规律,以及氟离子对鱼体生长的影响.结果表明,随着氟离子浓度的增加和暴露时间的延长,氟在西伯利亚鲟稚鱼硬骨和软骨中的含量显著增加,暴露90d时各暴露组硬骨和软骨中氟含量均显著高于对照组;西伯利亚鲟稚鱼暴露在较高浓度氟离子(7.8、18.7和51.8mg·L-1)中90d,生长速度(体重)显著下降;经过30d清水培养后,较高浓度暴露组(18.7和51.8mg·L-1)西伯利亚鲟稚鱼硬骨的氟含量显著下降.由此结论:氟在西伯利亚鲟稚鱼硬骨和软骨组织中具有较高的生物蓄积作用;转移至清水中饲养后,蓄积的高浓度的氟可从硬骨中排出.     

Sea-Cage Aquaculture, Sea Lice, and Declines of Wild Fish

Abstract: A sea cage, sometimes referred to as a net pen, is an enclosure designed to prevent farm fish from escaping and to protect them from large predators, while allowing a free flow of water through the cage to carry away waste. Farm fish thus share water with wild fish, which enables transmission of parasites, such as sea lice, from wild to farm and farm to wild fishes. Sea lice epidemics, together with recently documented population‐level declines of wild salmon in areas of sea‐cage farming, are a reminder that sea‐cage aquaculture is fundamentally different from terrestrial animal culture. The difference is that sea cages protect farm fish from the usual pathogen‐control mechanisms of nature, such as predators, but not from the pathogens themselves. A sea cage thus becomes an unintended pathogen factory. Basic physical theory explains why sea‐cage aquaculture causes sea lice on sympatric wild fish to increase and why increased lice burdens cause wild fish to decline, with extirpation as a real possibility. Theory is important to this issue because slow declines of wild fish can be difficult to detect amid large fluctuations from other causes. The important theoretical concepts are equilibrium, host‐density effect, reservoir‐host effect, and critical stocking level of farmed fish (stocking level at which lice proliferate on farm fish even if wild fish are not present to infect them). I explored these concepts and their implications without mathematics through examples from salmon farming. I also considered whether the lice‐control techniques used by sea‐cage farmers (medication and shortened grow‐out times) are capable of protecting wild fish. Elementary probability showed that (where W is the abundance of wild fish, W* is the prefarm abundance, F is the abundance of farm fish, and is the ratio of lice per farm fish to lice per wild fish). Declines of wild fish can be reduced by short growing cycles for farm fish, medicating farm fish, and keeping farm stocking levels low. Declines can be avoided only by ensuring that wild fish do not share water with farmed fish, either by locating sea cages very far from wild fish or through the use of closed‐containment aquaculture systems. These principles are likely to govern any aquaculture system where cage‐protected farm hosts and sympatric wild hosts have a common parasite with a direct life cycle.     

Documenting Loss of Large Trophy Fish from the Florida Keys with Historical Photographs

Abstract:  A loss of large vertebrates has occurred in aquatic and terrestrial ecosystems, but data to measure long-term population changes are sparse. Historical photographs provide visual and quantitative evidence of changes in mean individual size and species composition for groups of marine fish that have been targeted by sport fishing. I measured such trends for 13 groups of recreationally caught "trophy" reef fish with photographs taken in Key West, Florida, from 1956 to 2007. The mean fish size declined from an estimated 19.9 kg (SE 1.5) to 2.3 kg (SE 0.3), and there was a major shift in species composition. Landings from 1956 to 1960 were dominated by large groupers ( Epinephelus spp.), and other large predatory fish were commonly caught, including sharks with an average length of just <2 m. In contrast, landings in 2007 were composed of small snappers ( Lutjanus spp. and Ocyurus chrysurus ) with an average length of 34.4 cm (SE 0.62), and the average length of sharks declined by more than 50% over 50 years. Major declines in the size of fish caught were not reflected in the price of fishing trips, so customers paid the same amount for a less-valuable product. Historical photographs provide a window into a more pristine coral reef ecosystem that existed a half a century ago and lend support to current observations that unfished reef communities are able to support large numbers of large-bodied fish.     

胡萝卜鲢鱼丸子的研制

通过对胡萝卜鲢鱼丸子的配方和制作工艺试验,得出了鱼肉、肥膘、淀粉、盐分及胡萝卜颗粒的最佳配比,使产品达到营养化、功能化、方便化的目的。     

葛洲坝上下游江段鱼类时空分布特征研究

2009年6月和11月在葛洲坝上下游江段使用SIMRAD EY60回声探测仪对鱼类时空分布进行水声学调查。结果显示,葛洲坝上下游江段鱼类密度范围分别为2.8～122.7、8.8～888.8 ind./1 000 m3。上下游江段鱼类呈区域性分布,主要集中在西陵峡口、大江电站下游及三江等水域。大江电站下游流水区,鱼类一直集中在中下层。而在其它的静水和缓流区,6月份鱼类主要分布在中上层水域,11月份鱼类较为集中在中下层。6月份鱼类体长与分布水深无相关性（P>005）或负相关（P<005）,11月份体长与分布水深均呈正相关（P<005）。根据结果分析,由于葛洲坝上下游水文情势的差别,分布有不同生态类群的鱼类,因此形成区域性的水平分布。在静水和缓流区,垂直分布还存在季节间的变化。季节变化还对葛洲坝上下游江段鱼类体长与分布水深的关系有明显影响     

Is Biodiversity Friendly Fisheries Management Possible on Issyk-Kul Lake in the Kyrgyz Republic?

This paper aims to identify challenges, and threats, and further explore opportunities for a new Biodiversity Friendly Fisheries Management Regime on the Issyk-Kul Lake in the Kyrgyz Republic. This lake is the second largest high-altitude lake in the world providing recreational and small-scale fishing activities as well as cage culture of introduced species. The populations of several indigenous species are seriously threatened, because many of the introduced species are potential predators. We examine the root causes for overfishing and relationships of alien and endemic fish species in Issyk-Kul Lake and give possible policy options that can help remediate or mitigate the biodiversity degradation. This analysis focuses on necessary legal modifications, institutional cooperation, the protection of selected endemic fish species, control of the alien species, the sustainable extension services and management of fish ponds. Fisheries co-management is one option to explore shared stewardship and empowering user groups on the lake. A comprehensive fisheries management plan is also needed, in addition to immediate action and further studies on the following wider aspects: water management/irrigation issues, water-quality assessment near cage cultures, socio-cultural issues, resource inventory, and assessing fish biology and the lake ecosystem.