镇江长江豚类省级自然保护区水域生态修复效果的监测与评价

自2006年以来,长江豚类极度濒危的生存状况得到广泛关注,在其自然保护区实施一系列生态修复工程,为镇江长江豚类省级自然保护区内的江豚提供良好的生存环境。于2015—2018年在和畅洲水域建设生态浮岛、人工鱼巢和放流底栖动物进行水域生态修复,对生态修复工程进行跟踪监测和效果评价。结果表明：生态浮岛的建设可提高区域内浮游植物和浮游动物的生物多样性和群落结构复杂程度;人工鱼巢对产黏性卵鱼类具有一定增殖效果,增殖种类主要为鲤、鲫、䱗和黄尾鲴;生态浮岛和人工鱼巢的建设对鱼类均有较好的聚集效果;底栖动物增殖放流显著增加了放流物种的丰度、生物量及保护区底栖动物群落生物量,增殖放流效果评价为中等。该自然保护区水域生态修复效果明显,为工程施工影响下水生生物保护区生态修复提供科学依据。     

基于主成分分析的吸鱼泵对鱼类损伤评价方法

采用主成分分析法建立吸鱼泵的损伤综合评价方法,为吸鱼泵的研究与改进提供装备技术参数。使用真空吸鱼泵对鲫鱼进行吸捕试验,获取鱼体损伤数据。通过测定体表损伤面积比率、24 h存活率、红细胞数量、白细胞数量、超氧化物歧化酶(SOD)活力、谷丙转氨酶(ALT)活力、肌酐(Cr)含量等多个关键指标值,采用主成分分析法进行相关性分析,建立损伤综合评价模型。结果显示：采用主成分分析法提取出3个主成分的累积贡献率达到78.232%,可反映出鱼体损伤的大部分情况;损伤评价综合评价模型：F=0.285X₁+0.111X₂+0.316X₃+0.366X₄-0.118X₅+0.234X₆,真空吸鱼泵对鱼的体表和内脏无显著损伤情况,综合得分-0.102,与对照组接近,表明真空吸鱼泵对鱼的损伤影响很小。研究表明,SOD活力、白细胞数和体表损伤面积比率是对损伤评价影响较大的数据指标,采用主成分分析法建立的综合损伤评价模型可以作为评价鱼损伤情况的一种可行方法,为吸鱼泵的改进研究提供了有力参考。     

The decline of fisheries on the Madeira River,Brazil: The high cost of the hydroelectric dams in the Amazon Basin

Despite being considered beneficial by providing a clean and renewable source of energy, the construction of hydroelectric dams has extremely negative implications for Amazonian fisheries. This study investigated the impacts of the Santo Antônio and Jirau hydroelectric dams on the fishery stocks of the Madeira River. This investigation was based on fish catch data from the Z‐31 fishing colony, located in the municipality of Humaitá, in Amazonas State, Northern Brazil. Data were collected daily and provided information on the date of return from each trip, the fish species targeted, and the total catch (kg) between January 2002 and September 2017. The results indicated reductions of 39% in the mean annual catch and 34% in the mean monthly catches. These results highlight the high price paid by local fish communities for the development of hydroelectric power in the Amazon basin.     

Physical forcing on fish abundance in the southern California Current System

The California Current System (CCS) is an eastern boundary current system with strong biological productivity largely due to seasonal wind‐driven upwelling and transport of the California Current (CC). Two independent, yet complementary time series, CalCOFI ichthyoplankton surveys and sampling of southern California power plant cooling‐water intakes, have indicated that an assemblage of predominantly cool‐water affinity fishes spanning nearshore to oceanic environments in the southern CCS has declined dramatically from the 1970s to the 2000s. We examined potential oceanographic drivers behind this decline both within and north of the CalCOFI survey area in order to capture upstream processes as well. Empirical orthogonal function (EOF) analyses using output from a data‐assimilative regional ocean model revealed significant relationships between the fish time series and spatial patterns of upwelling, upper ocean heat content and eddy kinetic energy in the CCS. Correlation and linear regression analyses indicated that the declining trend in fish abundance was correlated with a suite of factors: reduced offshore and increased inshore upwelling; a long term warming trend combined with more recent interannual variability in ocean temperature; weaker eddy kinetic energy north of Point Conception (35°N), potentially indicating reduced transport of the California Current (CC); increased influence of the California Undercurrent (CUC); and a decline in zooplankton displacement volume across the southern CCS. Understanding how changes in oceanography affect fish populations will offer insights into managing fisheries in a changing climate.     

Fish‐processing wastes as an alternative diet for culturing the minute rotifer Proales similis de Beauchamp

We evaluated the suitability of fish waste diet (FWD) for culturing the minute rotifer Proales similis through the observation of their population growth and particle size selective feeding. A total of five treatments either with Nannochloropsis oculata or FWD (0.75 and 0.50 g/L) or the combination of N. oculata and FWD were set up in triplicates. P. similis were cultured in diluted natural seawater (8 g/L salinity) and 26 ± 1°C with the diet treatments being applied randomly. We daily monitored the rotifer density, the number of bacteria and the water quality in all the cultures. The population density of P. similis increased exponentially in all treatments, while the mean growth in FWD 0.75 g/L was significantly higher (p < .05) than that in the control. Addition of N. oculata to FWD resulted to lowered P. similis population growth. Bacterial colony count was high in FWD and introduction of P. similis to the diet decreased their density. The estimated bacteria ingestion rates were generally in the range of 6.03 × 10²–1.24 × 10⁴ bacteria/rotifer/hr and there was a positive linear relationship between bacterivory and rotifer population growth. We also observed a shift in the particle size distribution with a reduction in the frequency and concentration of small‐sized particles (<2.5 μm) at day 6. These results accentuate the potential of fish‐processing waste as diet for culturing P. similis which feeds on bacteria and small particles (≤2.5 μm) that are by‐products of degradation of this diet.     

Prevalence,intensity and histopathology of Zeylanicobdella arugamensis infestation on groupers reared on different aquaculture systems

The marine leech, Zeylanicobdella arugamensis, is a major threat to aquaculture in grouper-producing countries including Indonesia. This study aimed at investigating prevalence, intensity and histopathology of the ectoparasite in humpback and hybrid groupers cultured in different rearing systems. A total of 260 groupers (60 humpback groupers and 200 hybrid groupers) were used for samples. The marine leech was observed on skin, fins, gills and mouth, followed by histopathological assay on the skin tissue. The results showed that prevalence of the leech in both groupers was higher when they were cultured in the floating net cages compared with the hatchery, p < .05. Furthermore, humpback grouper had a higher prevalence than hybrid grouper when they were cultured in a similar system, p < .05. Meanwhile, there was no significant difference in intensity between the two groupers, p > .05. Within the hybrid groupers, the highest prevalence was obtained from hybrid groupers reared in the earthen ponds. Histopathological studies showed that the infected groupers exhibited inflammation, congestion and erosion of the epidermis layer. Hybrid grouper had more severe histopathological lesions in the skin tissues. These results suggested that species and type of aquaculture system had significantly determined the prevalence, intensity and severity of lesion in Z. arugamensis infestation.     

Habitat associations of the Threatened pugnose minnow (Opsopoeodus emiliae) at the northern edge of the species range

Pugnose minnow (Opsopoeodus emiliae) is a small, reclusive species that is widespread in North America, but is one of the rarest fishes in Canada, found in less than 12 known localities in southwestern Ontario. In contrast to most pugnose minnow populations across the global range, Canadian populations are primarily found in turbid systems, potentially indicating persistence in suboptimal conditions. We used data from a multi-gear species and habitat survey in the Canard River, Ontario, a system dominated by agricultural inputs and the best-known capture site of the species in Canada, to parameterise multi-gear occupancy models for understanding the relationship between pugnose minnow occupancy and microhabitat features, including the role of turbidity. Almost 300 pugnose minnow were captured, representing the largest single collection of the species in Canadian history. The best occupancy model indicated that the probability of pugnose minnow occupancy was highest in the deepest sites with the lowest water clarity (i.e. high turbidity); however, competing models suggested that occupancy was highest at sites with wild celery (Vallisneria americana) and higher water clarity, signifying that habitats with low turbidity may be utilised if sufficient physical cover exists. Together, our results suggest that Canadian pugnose minnow populations occupy and potentially favour turbid conditions, possibly to avoid visual predators in clearer habitats. It remains uncertain whether this abiotic association represents a long-term, viable, local adaptation or whether persistence of pugnose minnow in the Canard River is at risk unless significant water quality improvements can be made.     

Dietary β‐carotene improves growth performance and antioxidant status of juvenile Piaractus mesopotamicus

This study was conducted to investigate the effects of dietary synthetic β‐carotene on growth performance, haematological and immunological parameters, energy reserves and antioxidant status of juvenile fish Piaractus mesopotamicus. Two hundred and ten fish (12.24 ± 2.98 g) were fed with a control extruded feed (CEF) and the same diet supplemented with β‐carotene (BEF) for 90 days. A higher weight gain and specific growth rate were found in fish fed BEF in comparison with those fed CEF. In addition, BEF‐fed fish showed lower liver somatic index and a higher percentage of eosinophils. No statistical differences were found in energy reserves, except for plasma triglycerides which decreased in fish fed with BEF. Regarding oxidative stress markers, decreased activities of antioxidant enzymes were found in intestine and gills of BEF‐fed fish (SOD and GST, respectively). In the liver, both LPO levels and CAT activity decreased in fish fed with BEF. Additionally, lower brain LPO levels without changes in the antioxidant enzymes were observed in BEF‐fed fish. The inclusion of dietary synthetic β‐carotene improved growth and antioxidant status, and had a plasma triglyceride‐lowering effect in juvenile P. mesopotamicus.     

人类活动对大亚湾海域鱼类群落多样性及其演替的影响

根据2015—2016年间对大亚湾海域进行的4个航次底拖网调查数据,分析了大亚湾鱼类群落的种类组成和多样性特征。结果表明,调查共采集到鱼类131种,隶属14目、53科、84属。其中以鲈形目(Perciformes)占绝对优势(54.20%),其次是鳗鲡目(Agunilliformes)和鲽形目(Pleuronectiformes),均占9.92%。种类数具明显季节变化,以夏季最高,69种;春季最低,32种。鱼类群落优势种组成主要以二长棘犁齿鲷(Evynnis cardinalis)、李氏(Callionymus richardsoni)、斑(Clupanodon punctatus)、竹荚鱼(Trachurus japonicus)、黄鳍马面鲀(Thamnaconus hypargyreus)、短吻鲾(Leiognathus brevirostris)和细条天竺鲷(Apogon lineatus)等小型鱼类为主。多样性分析显示,鱼类物种多样性存在明显的季节差异和空间差异。季节变化上,多样性指数(H')季节变化范围为1.516~1.998,以冬季最高,秋季最低;均匀度指数(J')季节变化范围为0.494~0.869,以冬季最高,夏季最低;丰富度指数(D')季节变化范围为2.230~3.777,以夏季最高,秋季最低。典范对应分析表明,温度、盐度和水深是影响大亚湾海域鱼类群落结构的主要环境因子。空间分布上,海湾中部海域鱼类多样性水平高于沿岸海域。与历史资料相比,由于人类活动对大亚湾生态系统的干扰,鱼类群落结构发生了较大变化,优势种组成更替明显,多样性水平降低,鱼类群落结构趋向简单化。     

What can we learn by studying dead fish fry?

This study investigated the influence of temperature (4, 8 and 12°C) on development and survival of brown trout (Salmo trutta) fry. The three aims of this study were: (a) to propose a typology of malformations; (b) to compare malformation types between live and dead fry and (c) to establish relationships between temperature and malformation occurrences. It was found 20 single malformations and 39 combinations of two or more malformations. Comparison between dead and live fry at different development stages (hatching, emergence and first food intake) showed that malformations of yolk sac were predominant at hatching and then decreased, while malformations of skeleton or multiple malformations were higher thereafter. All dead fry, and only 14% of live fry were malformed. Dead fry were mainly characterized by yolk sac malformations and multiple malformations whatever the temperature. Live fry showed a higher rate of skeleton malformations at 12°C, and the different types of malformations were equally represented at two other temperatures (4 and 8°C). To conclude, it is suggested that some malformations (yolk sac at hatching, yolk sac associated with skeleton malformations at emergence and skeleton at first food intake or combinations of malformations at all stages)might be lethal as they were founding dead fry and that temperature influences differently the occurrence of malformations.