In situ video observations of benthic megafauna and fishes from the deep eastern Mediterranean Sea off Egypt

Remotely operated vehicle (ROV) video observations were used to document benthic fauna at a hydrocarbon drilling location, at 2 720 m depth, in the poorly studied deep water off northern Egypt. The decapod Chaceon mediterraneus was the most common organism at the site and the only benthic megafaunal invertebrate observed. Three species of fish, Coryphaenoides mediterraneus, Cataetyx laticeps and Bathypterois mediterraneus, were also encountered. These findings confirmed these three species as the deepest-distributed benthic fish in the eastern Mediterranean, and confirmed that the deep Mediterranean, in particular the eastern basin, is one of the world's poorest deep-sea ecosystems in terms of diversity. The behaviour exhibited by the species observed was consistent with their natatory capacity, deduced from their feeding intensity (gut fullness) and diet (mainly suprabenthic prey were consumed), and conservative life strategies adapted to an extremely low energy environment.     

Validation of the periodicity of opaque zone formation in the otoliths of four temperate reef fish from South Africa

An oxytetracycline (OTC) marker was used to validate the periodicity of opaque zone deposition in the otoliths of Chrysoblephus laticeps, Cheimerius nufar, Cymatoceps nasutus (Sparidae) and Dichistius capensis (Dichistiidae) in the wild. Fish were injected with OTC and tagged with external dart tags within a research fishing area of the Tsitsikamma National Park marine reserve on the southern Cape coast of South Africa. Recaptured fish, injected with OTC, were at liberty for between 711 and 2 102 days. Examination of their otoliths revealed that all deposited one opaque zone each year. The study confirmed the age estimates from previous studies that made use of marginal zone analysis as a validation method.     

Occurrence patterns of mesopelagic fish larvae in Sagami Bay, central Japan

The species composition, seasonal abundance, and vertical distribution of mesopelagic fish larvae are described based on discrete depth sampling from the surface down to 1000 m depth during four cruises at a fixed sampling station in Sagami Bay. The abundances of total mesopelagic fish larvae in April, July, September, and December were 65.7, 13.6, 118.9, and 17.2 individuals per 10 m² sea surface, respectively. Twenty species or types of mesopelagic fish larvae belonging to 10 families were collected. Diaphus garmani, Lipolagus ochotensis, Diogenichthys atlanticus, Sigmops gracile, and Maurolicus japonicus were the five most abundant larvae and accounted for 43.1, 14.5, 7.4, 6.3, and 5.9% of the total mesopelagic fish larvae, respectively. These five species showed clear seasonal changes in abundance, i.e. L. ochotensis, D. atlanticus, and S. gracile larvae mainly occurred during winter— spring; D. garmani and M. japonicus were collected during summer—autumn. No obvious diel vertical migration was found in these larvae. The larvae of D. garmani and M. japonicus were concentrated in the 25–50 and 50–100 m depth layers, respectively. The transforming stage of L. ochotensis, S. gracile, and D. atlanticus occurred at 400–1000 m depth, while their larvae (<8 mm standard length) occurred in the upper 100 m layer, indicating that metamorphosis of these species takes place in the 400–1000 m layer. Based on the occurrence of mesopelagic fish larvae and oceanographic processes in Sagami Bay, with the exception of D. garmani and M. japonicus, most larvae are considered to originate from the Kuroshio region where their main spawning grounds are formed.     

Distribution depth of the transforming stage larvae of myctophid fishes in the subtropical–tropical waters of the western North Pacific

We describe the day–night vertical distribution patterns of 18 species or types of myctophid fish larvae at the transforming stage based on discrete depth sampling from the surface down to 1000-m depth in the subtropical–tropical western North Pacific. A total of 551 transforming stage larvae were collected at the 19 sampling stations. Except for the Diaphus species and Notolychnus valdiviae, all of the transforming stage larvae (including genera Benthosema, Bolinichthys, Centrobranchus, Ceratoscopelus, Diogenichthys, Hygophum, Lampanyctus, Lobianchia, Myctophum, Symbolophorus, and Triphoturus) were collected in the lower mesopelagic zone from 600- to 900-m depth during both day and night, showing no diel vertical migration (DVM). On the contrary, the Diaphus species and N. valdiviae larvae undergo DVM during the transforming stage, occurring below 200-m layer during the daytime and migrating up to the upper 150-m layer at night, i.e., they show earlier adaptation to juvenile–adult behaviors. Most myctophid fish larvae are known to undertake substantial ontogenetic vertical migration (OVM) from the epipelagic to mesopelagic zones during their early life stage. Although considerable sampling effort was carried out in this study, transforming larvae, except for the above two migratory ones, were not collected in the epipelagic and upper mesopelagic zones, strongly suggesting that their sinking speed would be high. It would be advantageous for survival to spend their highly vulnerable transforming stage in the lower mesopelagic zone, where predation pressures are lower and physical conditions are more stable than in the upper layers.     

浙江南部近海春季鱼类群落结构特征及其年际变化

根据2016年和2020年5月在浙江南部近海采集的渔业资源调查资料,采用相对重要性指数、Bray-Curtis聚类和相似性百分比SIMPER分析、生物量谱及ABC曲线等方法,分析该水域春季鱼类群落结构特征及其稳定性的年际变化。结果显示:(1)2016年春季共捕获鱼类65种,优势种为带鱼Trichiurus lepturus、七星底灯鱼Benthosema pterotum和鳀Engraulis japonicus,而2020年春季共捕获鱼类30种,优势种为七星底灯鱼和带鱼;(2)通过聚类分析发现,2016和2020年春季鱼类群落空间格局相似,均可划分为南、北群落;(3)通过SIMPER分析,2016年春季南部群落典型种为二长棘鲷Evynnis cardinalis、龙头鱼Harpadon nehereus和鳀,北部群落典型种为龙头鱼,群落间的分歧种为带鱼;2020年南部群落典型种为七星底灯鱼,北部群落典型种为镰鲳Pampus echinogaster和小黄鱼Larimichthys polyactis,群落间的分歧种为带鱼、镰鲳和小黄鱼;(4)基于生物量谱分析,2016年和2020年春季鱼类标准生物量谱的斜率均小于-1,表明生物量均随个体平均体质量的增加而减少;(5)ABC曲线结果表明,2016年春季鱼类群落处于中等干扰状态(W=-0.22),而2020年春季鱼类群落则处于严重干扰状态(W=-0.09);(6) 经RDA排序分析,2016年和2020年春季影响鱼类群落分布的主要环境因子均为表层水温、盐度和水深。综上所述,浙江南部近海的鱼类年际变化为鱼类种类显著下降,群落特征种更替明显,群落受外界干扰影响加剧。     

Day–night variations in the demersal nekton assemblage on the Mediterranean shelf-break

The composition of the demersal nekton assemblage inhabiting the Mediterranean shelf-break of west-central Italy was examined to investigate the diel variation in species composition and abundance. Fish were obtained during four 24-h sampling periods that represented the four annual seasons. Thirty-two hauls (eight in each season) were conducted in a shelf-break area at 140–160 m depth. The density of fish, crustaceans, and decapods exhibited differences on short- and long-term time scales: multidimensional scaling suggested that season and light intensity may be important factors influencing fish assemblage composition.At the diel scale two main assemblages separating nocturnal and diurnal hauls were identified. The typical assemblage structure of shelf-break bottoms was represented during daylight by species such as Merluccius merluccius, Capros aper, Serranus hepatus, Macroramphosus scolopax and Trisopterus minutus capelanus. At night, the assemblage showed a drastic change due to the increase of small nektobenthic species, Argentina sphyraena and Glossanodon leioglossus, together with cave-dwelling fish (Gnathophis mystax, Chlopsis bicolor, Nettastoma melanurum) and nektobenthic crustaceans (i.e., Parapenaeus longirostris and Solenocera membranacea).The above-mentioned differences in species composition may be related to changes in vertical distribution for trophic needs (M. merluccius) and/or in the shoal structure (A. sphyraena and G. leioglossus). The lack of data on the pattern of trawl catchability of Mediterranean species during the day may lead to an inaccurate estimation of species abundance when only diurnal trawl survey data are used.     

Do the shallow‐water habitats of a hypersaline tropical estuary act as nursery grounds for fishes?

Fish assemblages were studied in a hypersaline tropical estuary in Northeastern Brazil. A total of 104 species were collected by beach seine during the dry and rainy seasons of 2012. Two families, Atherinopsidae and Gerreidae, were numerically dominant in all zones of the estuary; juveniles of Atherinella brasiliensis, Eucinostomus argenteus, Lile piquitinga, Ulaema lefroyi, Lutjanus analis and Sphoeroides greeleyi contributed 77% of the total catch. The factors that best explained the fish abundance pattern were salinity and depth, which were related to spatial segregation. Species richness was lowest in the upper zone, an area with high salinity and shallow depth. The distinct roles of structurally different habitats (submerged macrophyte beds and mangrove prop‐roots) and the influence of physicochemical conditions in the middle zone of the estuary may influence taxonomic diversity. The middle zone of the estuary is the one most attractive to juveniles of reef species (Lutjanidae and Serranidae). The fish assemblages are clearly dominated by marine estuarine dependent species, highlighting the importance of the ecosystem as a nursery ground for marine species of the Brazilian coast.     

福建三沙湾游泳动物种类和数量的季节变化

根据2019年1月、4月、7月和10月四个季度10个站位定置张网调查资料, 对福建三沙湾游泳动物的种类组成及季节变化进行分析研究。结果表明: 调查共获得游泳动物209种, 隶属于3门4纲19目73科144属, 其中鱼类154种, 甲壳类48种, 头足类7种。游泳动物种类数以秋季出现最多, 四个季节共同出现的种类有42种。鲈形目种类最多, 其次是十足目。鱼类适温性以暖水性种类居多, 占71.43%, 暖温性种类次之(27.92%); 生态类型以底层、近底层鱼类居多, 两者合占75.97%。鹰爪虾(Trachypenaeus curvirostris)、大黄鱼(Larimichthys crocea)、棘头梅童鱼(Collichthys lucidus)、红星梭子蟹(Portunus sanguinolentus)和日本蟳(Charybdis japonica)等14个种类是三沙湾游泳动物的优势种类, 季节性优势种居多。三沙湾定置张网调查渔业资源质量密度为111.09 kg/km², 尾数密度为13.72×10³ ind./km², 均以夏季最高, 春季最低。应该进一步加强对三沙湾渔业资源的合理利用和有效保护, 同时重视对外来物种的监测。     

浙江南部沿岸产卵场春、夏季鱼卵、仔稚鱼种类组成与分布

根据2011年4月、5月与6月对浙江南部沿岸产卵场进行的共3个航次的调查资料,对该海域的鱼卵、仔稚鱼的种类组成和数量分布进行了分析,结果表明,共发现鱼卵、仔稚鱼72个种类,分别隶属11目38科48属。其中鱼卵29种,分别隶属6目18科24属;仔稚鱼55种,分别隶属10目29科40属。4—6月仔稚鱼数量呈逐月递减的趋势,而鱼卵数量6月最多,5月最少。鱼卵优势种4月以斑鰶、棱鱚、小黄鱼与蓝点马鲛为主,5月以斑鰶、鳀、龙头鱼、银鲳、蓝点马鲛与石首鱼科为主,6月以鳀、龙头鱼、多鳞鱚与鲱科鱼类为主;仔稚鱼优势种4月以虾虎鱼类、褐菖鲉与平鲉科为主,5月以鳀、虾虎鱼类、棱鱚、斑鰶与长鳍篮子鱼为主,6月以鳀与虾虎鱼类为主。斑鰶、鲳鱼、小黄鱼、棱鱚、蓝点马鲛与褐菖鲉的产卵盛期为4月,而鳀与龙头鱼的产卵盛期为6月。     

Use of submerged aquatic vegetation as habitat by young-of-the-year epibenthic fishes in shallow Maine nearshore waters

Epibenthic fishes were collected with daytime beam trawl tows (n = 1713) in three shallow (<10 m) habitats of submerged aquatic vegetation (SAV), Zostera marina (eelgrass), Laminaria longicruris (kelp), Phyllophora sp. (algae), and unvegetated sandy/mud areas. We divided the Maine coast into three broad zones based upon geological features and sampled over five consecutive years; during April–November 2000 in the mid coast, in 2001 and 2002 along the south coast and in 2003 and 2004 along the eastern Maine coast. We quantified habitat use by eight economically important fish species (Gadus morhua, Microgadus tomcod, Pollachius virens, Urophycis chuss, Urophycis tenuis, Osmerus mordax, Tautogolabrus adspersus, and Pseudopleuronectes americanus) and 10 other common epibenthic species (n = 18 571). We identified the physical and biological variables most important in discriminating between habitats with and without individual fish species. Logistic regression models based on nearshore habitat characteristics were developed to predict the distribution of these species along the three zones representing broad geological regions of the Maine coast. Logistic regression models correctly classified individual fish species 58.7–97.1% of the time based on the temporal and physical habitat variables (month, temperature, salinity, and depth) and the presence–absence of submerged aquatic vegetation (Zostera, Laminaria, or Phyllophora). Overall fish presence and economically important fish presence were correctly classified 61.1–79.8% and 66.0–73.6% of the time, respectively. The Maine shallow water fish community was composed primarily of young-of-the-year and juvenile fishes with all habitats functioning as facultative nursery areas. Presence of most fish species was positively associated with Zostera, Laminaria, and to a lesser extent, Phyllophora. This study provides direct evidence of shallow waters of the Gulf of Maine as critical facultative nursery habitat for juvenile G. morhua, M. tomcod, P. virens, U. tenuis, U. chuss, T. adspersus, O. mordax and P. americanus, and many ecologically important species.     

春季长江口外海底层鱼类群聚特征及其与环境因子的关系

为了研究春季长江口外海底层鱼类群聚特征及其与环境因子的关系,我们根据2015年5月长江口外海底层鱼类的调查资料,使用聚类分析(Cluster)、非参数多维标度排序(NMDS)、相似性分析(ANOSIM)、相似性百分比分析(SIMPER)以及典型对应分析(CCA)等方法对资料进行分析。本研究共记录底层鱼类58种,其中鲈形目种类数最多(21种),鲽形目次之。六丝钝尾虾虎鱼(Amblychaeturichthys hexanema)是优势种。底层鱼类可以划分为3个群组—近海组、南部中间组和南部远海组,不同群组的物种组成差异显著。南部中间组和南部远海组的物种多为东海外海种类,这可能是近岸黑潮底层分支影响的结果。物种数、Margalef丰富度、Shannon-Wiener多样性和Pielou均匀度从近海到与远海呈逐渐增加的趋势。CCA分析表明深度是显著影响底层鱼类的环境因子。短鳄齿鱼(Champsodon snyderi)、丝鳍(Repomucenus virgis)、多棘腔吻鳕(Coelorinchus multispinulosus)等东海外海种类与深度呈正相关,而优势种六丝钝尾虾虎鱼受环境因子影响较小。     

Do Mediterranean fish assemblages associated with marine caves and rocky cliffs differ?

Fish assemblages associated with marine caves and rocky cliffs were investigated in the Salento Peninsula (SE Italy, Mediterranean Sea) by using visual census methods. Sampling was done at three sites, each of which included 4 habitat types: the external and the internal portions of caves, and shallow and deep rocky cliffs. 10 and 13 species were found exclusively inside cave habitats (e.g. Corcyrogobius lichtensteini, Thorogobius ephippiatus and Grammonus ater) or in rocky cliffs (e.g. Diplodus annularis, Sarpa salpa, Sparisoma cretense, Spondyliosoma cantharus), respectively. The four habitat types shared 10 species, and the external portions of the caves shared the most species (both with the internal cave portions and the external rocky cliffs). As a general rule, dissimilarity in the fish assemblage structure between habitats was far greater than dissimilarity between sites. Apogon imberbis (mostly associated with caves) and Chromis chromis (typifying rocky cliffs, mainly the deep ones) mostly contributed to dissimilarities between caves and rocky cliffs. Apogon imberbis (mostly associated with internal caves) and Coris julis (mainly associated to external cave portions) contributed strongly to dissimilarities between internal and external cave portions, while C. chromis, Symphodus mediterraneus and C. julis (associated with the deeper cliffs) and Thalassoma pavo (mostly present in shallow cliffs) differentiated deep and shallow cliffs. Diplodus vulgaris, Oblada melanura and Mullus surmuletus showed a marked increase in density during the cold season in the caves. These results show that fish assemblages associated with rocky reefs rich in marine caves (in terms of relative densities, species composition, species richness, exclusive species and presence of juveniles of some valuable species) may be affected by the peculiar ecological conditions within caves, which could provide additional resources for fishes (e.g. food availability, refuge against predators, sand patches within a rocky matrix) compared to rocky reefs without caves. These results suggest that stretches of rocky coasts rich in marine caves should be considered within management/conservation programs (e.g. when establishing Marine Protected Areas).     

Influence of rock‐pool characteristics on the distribution and abundance of inter‐tidal fishes

Rock pools can be found in inter‐tidal marine environments worldwide; however, there have been few studies exploring what drives their, fish species composition, especially in Australia. The rock‐pool environment is highly dynamic and offers a unique natural laboratory to study the habitat choices, physiological limitations and adaptations of inter‐tidal fish species. In this study rock pools of the Sydney region were sampled to determine how the physical (volume, depth, rock cover and vertical position) and biological (algal cover and predator presence) parameters of pools influence fish distribution and abundance. A total of 27 fish species representing 14 families was observed in tide pools at the four study locations. The five most abundant species were Bathygobius cocosensis, Centropogon australis, Enneapterygius atrogulare, Lepidoblennius haplodactylus and Microcanthus strigatus, which together represented 71% of the total number of fish recorded. Larger rock pools containing more algal and rock ledge cover hosted a larger and more diverse population of fish. Furthermore, certain species were only found in pools with specific characteristics, such as the presence of loose shells, a variety algae or rock cover, suggesting a high degree of habitat specificity. By contrast, some species were ubiquitous and thus can likely tolerate a wide variety of physical conditions.     

Post-release survival and feeding in reared turbot

As part of the Danish restocking program, an experiment was carried out with four groups of turbot Psetta maxima released on two different occasions at the same location in Århus Bay, Denmark. One objective was to analyse the duration of post-release mortality and the magnitude of this mortality. In 2003 a group called Large turbot (17.1 cm total length (L_T)) and a group called Intermediate (L_T = 11.8 cm) were released, and in 2004 two similar-sized groups called Naive and Conditioned (L_T = 9.8 cm) were released. The Conditioned differed from the Naive turbot by being transferred to enclosures at the release location six days prior to the actual release. This experiment was performed to investigate whether such a conditioning period had a positive effect on the survival and hence the success of the stocking. All the groups released were monitored daily until day 8, using a juvenile flatfish-trawl to recapture the fish. The catches were analyzed on the basis of a normal distribution approximation method, founded in diffusion theory, from which daily abundance of the released fish and hence post-release mortality could be estimated. The group of Large turbot suffered negligible post-release mortality, but for the Conditioned, Naive and Intermediate groups the loss varied between 34 and 66% d^− 1. The mortality for the Conditioned group was found to be half that of the Naive turbot released simultaneously. The period of high post-release mortality was estimated to be restricted to three days after release. The only active predators observed in the area were birds. Besides estimating mortality the diffusion model provides an estimate on the catchability of the released turbot when fished with a juvenile flatfish-trawl. Catchabilities varied between 38 and 52% for all releases except for the 17 cm sized turbot released, where catchability was only 12%. The feeding performance of the released fish was also analysed and compared with that of wild fish caught at the same location. These results showed that the proportion of stomachs containing food increased not only with time after release, but also with the size of the turbot. However, whether or not fish was included in the diet was not related to size but to time after release and to whether they had been conditioned or not.     

Food utilisation by coastal fish assemblages in rocky and soft bottoms on the Swedish west coast: Inference for identification of essential fish habitats

The concept of essential fish habitats (EFHs) is widely accepted for conservational and management purposes. EFHs are often considered as high quality habitats for fisheries species and subsequently of high values for society. In this study, fish and Substrate-Associated Prey (SAP) were sampled during the productive summer season 1998 (fish) and 2003 and 2004 (SAP) in shallow coastal rocky- and soft-bottom habitats on the Swedish west coast. The aim was to study the spatial and monthly variation of SAP as well as abundance and biomass of fish, and to examine if food items found in the diet of the fish assemblage were derived from SAP. We also examined if the diet of Ctenolabrus rupestris, a resident and abundant fish species in the shallow coastal habitats, and the diet of four seasonally abundant and commercially important fish species (Gadus morhua, Pleuronectes platessa, Salmo trutta and Scomber scombrus) were derived from SAP. There were significantly higher mean species number and abundance of the SAP assemblage on rocky compared to soft bottoms and the highest values were found on the rocky bottoms in August and in the shallowest (0–3 m) depth strata. There were no significant differences in number of fish species caught in the two habitats, although mean number of fish and mean biomass were significantly higher on rocky bottoms. Both habitats showed the same seasonal variation and the highest values of number of fish species, abundance and biomass were observed in June. On rocky bottoms, gastropods and amphipods were the most frequent food items in the diet of the entire fish assemblage and these items were also the most abundant SAP in this habitat. The dominant food items of the soft-bottom fish assemblage were decapods and fish, which were not common SAP. However, except for S. scombrus, the diet of the selected fish species showed a strong association to the SAP availability. Gadus morhua displayed the strongest association to SAP on rocky bottoms and P. platessa and C. rupestris to SAP on soft bottoms. Further, for C. rupestris, multivariate statistical analysis showed a significant association to the SAP assemblage on both rocky and soft bottoms. These results provide vital new information for the management and conservation of Essential Fish Habitats on the Swedish west coast.     

Heavy metals in some New Zealand commercial sea fishes

To establish a base line against which future pollution may be measured, eight common commercial species of New Zealand sea fish were analysed for cadmium, chromium, copper, iron, lead, manganese, nickel, and zinc. One sample of edible muscle tissue was analysed for each of 70 samples of each species. The internal organs of up to five specimens of each species were also analysed. The fish studied were: kahawai, Arripis trutta, trevally, Caranx lutescens, tarakihi, Cheilodactylis macropterus, snapper, Chrysophrys auratus, moki, Latridopsis ciliaris, hapuku, Polyprion oxygeneios, kingfish, Seriola grandis and gurnard, Trigla kumu.

Although, none of the edible parts of the fish appeared to have trace element levels likely to be a public health problem (cadmium 0.002–0.02 ppm, chromium 0.01–0.04 ppm, copper 0.04–0.95 ppm, iron 0.9–13.5 ppm, lead ‘ 0.14–0.95 ppm, manganese 0.04–2.00 ppm, nickel 0.01–0.08 ppm, zinc 2.0–36.0 ppm), some of the organs (particularly the liver) had relatively high concentrations of elements such as cadmium (up to 54 ppm). Only if some industry were to seek to exploit internal organs of fish for human consumption would such levels become important. There was some evidence for a relationship between trace element concentrations and fish size for copper in kingfish and snapper, iron in hapuku, manganese in gurnard, and for zinc in kingfish and tarakihi. Some element pairs such as copper and zinc, iron and manganese, appeared to have concentrations which were mutually related. It was assumed that the elemental concentrations reported represent natural levels and are not the result of significant man‐made pollution because there are no major industries or large urban centres adjacent to the fishing grounds.     

春、秋季东海大桥海上风电场水域鱼类群落结构

为探明工程建设后东海大桥风电场水域鱼类群落结构特征,作者利用等级聚类和多元统计等方法对该水域鱼类种类组成、优势种及群落结构进行分析。春、秋季共发现18种鱼类,隶属6目9科15属;鲈形目鱼类所占比例最高(50%),其中又以虾虎鱼科鱼类最高(44.4%)。春季优势种为短吻红舌鳎(Cynoglossus joyneri)、棘头梅童鱼(Collichthys lucidus)、矛尾虾虎鱼(Chaeturichthys stigmatias)和孔虾虎鱼(Trypauchen vagina),秋季优势种为棘头梅童鱼、龙头鱼(Harpadon nehereus)和凤鲚(Coilia mystus);棘头梅童鱼为春、秋季共同优势种。等级聚类和非度量多维标序排序表明,东海大桥风电场水域鱼类群落可分为春季和秋季2个组群,相似性检验(ANOSIM)显示2个组群差异极显著(R=0.851,P0.01)。生物与环境相关分析(BIOENV)表明温度和盐度是影响东海大桥风电场水域鱼类群落结构的最主要环境因子,两者结合因子与鱼类群落的相关系数为0.791。本研究发现,东海大桥风电场水域是棘头梅童鱼、凤鲚、龙头鱼等多种鱼类的育幼和索饵场所,群落结构具有典型的季节特征。     

养殖鲟鱼出血症病原鲁氏耶尔森菌的分离鉴定和致病性研究

鲁氏耶尔森菌(Yersinia ruckeri)是鲑鳟鱼类和温水性鱼类肠炎红嘴病的主要病原,可引起病鱼体表出血、肠道肿胀发炎等临床症状。本研究从患出血症施氏鲟(Acipenser schrenckii)中分离到一株致病性菌株(YR-H01),生理生化鉴定和16S rRNA基因序列分析表明YR-H01株为鲁氏耶尔森菌。人工感染该菌后发病鱼表现为肛门红肿、外突明显,部分鱼鳍基部和下颌处有出血现象,内脏器官不同程度出血,且从组织中再分离的细菌特性与原感染菌相同。腹腔注射后该菌株对施氏鲟的半致死浓度为7.2×106CFU,且攻毒剂量越大,临床病症出现越快。病理组织切片显示,该菌感染鲟鱼后肝细胞发生明显病变,淋巴细胞侵润,肝索结构消失,细胞肿胀,核空泡变性或核仁边缘化。     

莱州湾鱼卵、仔稚鱼数量分布及其与环境因子相关关系研究

于2007年和2008年6月、8月,用大型浮游生物网对莱州湾鱼卵、仔稚鱼种类组成与数量分布进行了4个航次调查。结果表明,采集到11271粒鱼卵,隶属于4目、15科、22种(不包括2个未定名物种);仔稚鱼2942尾,隶属于4目、9科、12种(不包括2个未定名物种)。6月份是莱州湾大部分鱼类主要产卵期,鱼卵、仔稚鱼种类达25种,鱼卵优势种以斑(Clupanodon punctatus)和凤鲚(Coilia mystus)为主;仔稚鱼优势种以凤鲚、梭鱼(Mugil soiuy)和斑为主。8月份产卵的鱼类较少,仅采集到15种鱼卵、仔稚鱼,优势种均以凤鲚和鲈鱼(Lateolabrax japonicus)为主。鱼卵、仔稚鱼平面分布极不均匀,黄河、广利河和老弥河口附近海域数量较多,莱州湾中部海域数量较少。通过SPSS软件分析发现,鱼卵数量与仔稚鱼、表层铵盐含量呈显著正相关(r=0.438,0.604,P0.01),与盐度、透明度呈负相关(r=-0.343,-0.329,P0.05);仔稚鱼数量仅与鱼卵数量和表层铵盐含量呈显著正相关(r=0.438,0.536,P0.01),与其它环境因子没有明显相关关系(P0.05)。     

Demersal fish assemblages off southern New Zealand in relation to depth and temperature

We examined the relationship between demersal fish assemblage and depth, temperature, latitude and longitude off southern New Zealand (46–54°S and 165–180°E) in water depths of 80–787 m. Catch weight data were analysed by two-way indicator analysis (TWIA), groupaverage agglomerative clustering (UPGMA) and Detrended Correspondence Analysis (DCA). The spatial pattern of demersal fish off southern New Zealand conforms to the concept of species groups or fish assemblages related to environmental gradients. Shallow-water assemblages were dominated by species from the families Gempylidae, Squalidae, Triakidae and Moridae, mainly represented by Thyrsites atun, Squalus acanthias, Galeorhinus australis, and Pseudophycis bachus. Deep water assemblages were dominated by Chimaeridae, Argentinidae, Merlucciidae and Macrouridae, mainly represented by Hydrolagus novaezelandiae, Argentina elongata, Macruronus novaezelandiae, and Lepidorhynchus denticulatus. Total catch weight was often dominated by Merlucciidae, Macrouridae and Gempylidae. Fish assemblages were related to discrete ranges of depth (< and >300 m) and temperature (< and >9.5°C), but the range of sediment types was too narrow to show any correlation.