Habitat preferences of selected demersal fish species in the Bay of Biscay and Celtic Sea, North-East Atlantic

According to the Ideal Free Distribution theory, individual fish are distributed where environmental conditions are optimal, and the occupied area may vary with population abundance. Thus, observed distributions are a combination of habitat suitability and density-dependent effects. Data from an annual bottom trawl survey taking place in autumn were used to assess associations between the distributions of eight demersal fish species, separately for juveniles and adults, and habitat characteristics (depth, temperature and salinity) in the Bay of Biscay and Celtic Sea. Cumulative distribution functions were used to describe the general frequency distributions of environmental variables and their relationships with fish density. During the period 1992–2006, observed bottom temperatures fluctuated with no time trend (ΔT = 8°C in the first 80 m) and population abundances varied significantly. Juvenile hake, poor cod, blue whiting, adult red gurnard, adult megrim, and lesser-spotted dogfish were found to be significantly associated with specific depth ranges. Associations with bottom temperature and salinity were weaker. For some species, preferred environmental conditions changed over time, independently of variations in environmental conditions. In general, most species seemed to be able to cope with the experienced range of conditions. Habitat associations were not influenced by abundance variations. Fluctuating abundances had an impact on spatial occupation only for red gurnard adults, lesser-spotted dogfish and blue whiting juveniles, independent of absolute densities.     

Habitat variability in young-of-the-year winter flounder, Pseudopleuronectes americanus, in Maine estuaries

The Magnuson-Stevens Fishery Conservation and Management Act defines essential fish habitat (EFH) as “the waters and substrate necessary to fish for spawning, breeding, feeding, and growth to maturity” and the protection of nursery areas has become a key element in US Federal fisheries management. Distribution and abundance by habitat for age-0, young-of-the-year (YOY) winter flounder, Pseudopleuronectes americanus, were compared for 28 Maine estuaries to help define essential fish habitat for this life history stage. The Maine coast was divided into three broad geographic zones based upon geological features and sampled over 5 consecutive years; during April–November of 2000 in the Mid-coast, in 2001 and 2002 along the Southwest coast and in 2003 and 2004 along the Eastern Maine coast. One beam trawl (2.0 m width, 3 mm mesh) sample was collected in one to four habitats in estuaries: eelgrass (Zostera marina), kelp (Laminaria longicruris), drift algae (Phyllophora sp.) and unvegetated sand/mud. Fish were sampled every 2 weeks, April–November 2000–2004. Abundance of YOY winter flounder was greatest in Mid-coast estuaries between Casco and Penobscot Bays and was significantly lower in Southwest and Eastern estuaries. Abundance was similar across all four habitats in Mid-coast estuaries in 2000. In the other years, YOY were found in higher abundance in eelgrass relative to other habitats. A logistic regression model based on nearshore habitat characteristics was developed to predict the distribution of this species along the three broad geological zones of the Maine coast with the physical and biological variables most important in discriminating between habitats with and without individual fish identified. This logistic regression model correctly classified winter flounder 72.4% of the time based on the year, zone, the physical habitat variables (temperature, salinity, depth) and the presence–absence of submerged aquatic vegetation (eelgrass, kelp or algae). These results indicate that the type of habitat most important to YOY winter flounder varies among estuaries and EFH for this species and life stage must be defined with care.     

Cohort‐specific variation in juvenile coho salmon habitat use

In this study, we examined summer and fall freshwater rearing habitat use by juvenile coho salmon (Oncorhynchus kisutch) in the quickly urbanising Big Lake drainage in south‐central Alaska. Habitat use was assessed by regressing fish count data against habitat survey information across thirty study sites using generalised linear mixed models. Habitat associations were examined by age‐0 and age‐1+ cohorts separately, providing an opportunity to compare habitat use across different juvenile coho salmon life stages during freshwater rearing. Regression results indicated that the age‐0 cohorts were strongly associated with shallow, wide stream reaches with in‐stream vegetation, whereas age‐1+ cohorts were associated with deeper stream reaches. Furthermore, associations between fork length and habitat characteristics suggest cohort‐specific habitat use patterns are distinct from those attributable to fish size. Habitat use information generated from this study is being used to guide optimal fish passage restoration planning in the Big Lake drainage. Evidence for habitat use partitioning by age cohort during freshwater juvenile rearing indicates that pooling age cohorts into a single “juvenile” stage for the purposes of watershed management may mask important habitat use dynamics.     

近30年渤海鱼类种群早期补充群体群聚特性和结构更替

基于30余年渤海鱼卵、仔稚鱼历史调查资料的整理分析并结合产卵场补充调查,以1982~1983年周年逐月调查资料为本底,采用多元统计学方法分析30余年渤海鱼类种群早期补充群体群聚特性(物种多样性和关键种群)的季节变化和年代际变化,并掌握结构更替过程中优势种和重要种协同消长规律。分析结果显示,渤海各调查季节(冬季除外)鱼卵、仔稚鱼种类数以及资源丰度指数呈先降后升变动趋势。当前鱼卵种类数仅为20世纪80年代1/2左右,资源丰度不足20世纪80年代的1/10;仔稚鱼种类数和资源丰度仅为20世纪80年代的3/4左右,但冬季仔稚鱼种类数和资源丰度指数呈现上升趋势。各调查时期相同季节鱼卵优势种变化不明显,但仔稚鱼优势种变化幅度超过鱼卵,底层重要经济种类早期补充群体优势度急剧下降;鱼卵和仔稚鱼物种多样性水平在升温季节较高而在降温季节较低,调查期内各季主要呈现先降后升变动趋势。鱼类早期补充群体种类更替现象明显,近年来种类更替率呈现明显加快趋势。各调查时期相同季节各适温类型产卵亲体种数均呈现先降后升变动趋势,但各适温类型种数所占比例和全年综合各适温类型种数所占比例基本稳定。各调查时期相同季节各主要栖所类型产卵亲体种类数也均呈现先降后升变动趋势,全年综合陆架浅水中上层鱼类种数所占比例升高,中底层和底层鱼类所占比例有所下降。近30年在多重外来干扰作用下,渤海鱼类早期补充过程各个关键环节已随其栖息地(产卵场)生境要素发生不可逆变化或变迁。渤海鱼类种群早期补充群体群聚特性和结构更替是环境-捕捞胁迫下鱼类群落内多重生态位的交替失调和渔业资源结构性衰退的具体表现。     

舟山崎头洋海域春秋季鱼类种类组成及数量分布

本研究利用2012年5月（春季）、10月（秋季）2个季度月的单船底拖网渔获的鱼类样品,对舟山渔场崎头洋海域鱼类种类组成、区系特点及数量分布等进行了研究。结果如下：（1）共获得鱼类50种,隶属于11目27科,以石首鱼科和缎虎鱼科的种类最多,各有7种,分别占总种数的14．0％;（2）根据适温性可将其划分为暖水性和暖温性2种适温类型,以暖温性为主,有36种,占鱼类总种数的72．0％;（3）春季主要集中在舟山本岛一小干岛海域,而秋季则集中在舟山本岛一小干岛海域以及穿山半岛一六横岛西南海域;（4）春季优势种有六丝矛尾锻虎鱼Chaeturichthys hexanema、带鱼Trichiurus haumela、鲈鱼Lateolabrax japonicus、棘头梅童鱼Collichthys lucidus、龙头鱼Harpodon nehereus等5种,而秋季优势种仅龙头鱼1种;（5）通过分析优势种的种群组成和底层温盐数据,发现该海域在春季可能为带鱼、棘头梅童鱼和鲈鱼等幼鱼的索饵场。     

Habitat use of age 0 Alabama shad in the Pascagoula River drainage, USA

Mickle PF, Schaefer JF, Adams SB, Kreiser BR. Habitat use of age 0 Alabama shad in the Pascagoula River drainage, USA. Ecology of Freshwater Fish 2010: 19: 107–115. © 2009 John Wiley & Sons A/S
Abstract – Alabama shad ( Alosa alabamae ) is an anadromous species that spawns in Gulf of Mexico drainages and is a NOAA Fisheries Species of Concern. Habitat degradation and barriers to migration are considered contributing factors to range contraction that has left just the Pascagoula River drainage population in Mississippi. We studied juvenile life history and autecology in three rivers within the drainage. We collected fish, habitat and physicochemical data in three habitat types (sandbar, open channel and bank) from June to October 2004–2006. Sandbar habitat was favoured by smaller individuals early in the year. Catch per unit effort (CPUE) decreased through the summer as larger fish began occupying bank and open channel habitat. The most parsimonious model of abundance included year and river variables, while patterns of presence and absence were best explained by river, habitat type and physiochemical variables. While all three rivers in the drainage contained Alabama shad, fish were less abundant and had lower condition values in the Chickasawhay River. Earlier work suggested the Alabama shad may gradually move downstream towards the Gulf of Mexico in their first year. However, we found no evidence of this and captured large fish high in the drainage late in the year.     

Size-related habitat use by bitterling (Rhodeus sericeus) in a regulated lowland river

Abstract  – Habitat use by four size-classes of bitterling ( Rhodeus sericeus ) in a regulated lowland river was studied at two spatial scales. Mesohabitat scale was represented by the bank type (boulder, beach and steep eroded bank). Microhabitat associations with substrate types, vegetation, woody debris and position in the stream were examined at each mesohabitat scale. Three size cohorts of young-of-the-year (0+) fish and a group of adult bitterling were detected. Univariate ( χ ²-tests) and multivariate (Outlying Mean Index analysis) methods were applied to determine size-related habitat associations. All the size-classes of bitterling avoided the steep eroded bank and most 0+ bitterling were distributed along the boulder bank. The smallest fish had the most pronounced habitat requirements and occurred mostly in the depositional areas, whereas the larger 0+ fish occurred in deeper water. The size-related change in the habitat use coincided with a change in diet and morphological state.     

长江口近海秋季鱼类资源的年变化分析

选用2002~2005年秋季长江口近海渔业资源和温盐度同步调查数据,对该水域秋季鱼类资源量指数、多样性指数、优势种组成以及水温、盐度的年间变化进行了分析,并对鱼类资源量与水温、盐度之间的关系进行了初步研究。结果表明:秋季长江口近海的鱼类资源量指数和多样性指数的年间变化均较为明显,但优势种组成较为稳定,以带鱼、小黄鱼、银鲳、刺鲳为主要优势种,且各年份基本上以带鱼和小黄鱼占有绝对的优势地位。当前长江口近海鱼类群落处于较低水平的相对稳定状态。秋季长江口近海鱼类的资源量和底层水温的变化趋势较为一致,而与表层水温的变化趋势呈现相反的趋势,同时和表底层的水温差变化呈负相关关系;鱼类资源量的变化受表层盐度的影响较为明显,它们之间呈现相同的变化趋势。     

Groundfish species associations with distinct oceanographic habitats in the Northern California Current

Ecosystem-based management places a strong emphasis on habitat, but little work has been done to examine how water column properties may influence the distribution, abundances and structure of groundfish assemblages. We identified and described oceanographic habitats in the northern California Current based on temperature, salinity, chlorophyll- a and the inherent variability in these factors. We then examined the distribution and the abundance of groundfishes in relation to these oceanographic habitats and conditions with the long-term goal of improving science for ecosystem-based management of the groundfish fishery of the west coast of the USA. Five summertime oceanographic habitats with distinct physical and biological characteristics were identified in the northeast Pacific Ocean off the northwest Coast of the USA: Offshore Habitat, Upwelling Habitat, Highly Variable Upwelling Habitat, River Plume Habitat, and Highly Variable Habitat. Overall, the species composition differed among the five oceanographic habitats, with certain groundfish species being highly indicative of some habitats; however, the majority of the associations were weak due to overlap of species distributions in the nearshore oceanographic habitats. In contrast, groundfish species showed strong associations with individual oceanographic factors, primarily depth, surface chlorophyll- a , and bottom salinity and temperature. In addition, latitudinal variations in upwelling intensity, river discharge and productivity led to the identification of three regions where high chlorophyll- a concentrations were associated with large abundances of specific groundfish species. The combined oceanographic datasets and data products that we produced have the potential to be a powerful tool for improving our knowledge of the west coast ecosystem.     

A spatially explicit, individual-based model to assess the role of estuarine nurseries in the early life history of North Sea herring, Clupea harengus

Herring (Clupea harengus) enter and remain within North Sea estuaries during well‐defined periods of their early life history. The costs and benefits of the migrations between offshore spawning grounds and upper, low‐salinity zones of estuarine nurseries are identified using a dynamic state‐variable model, in which the fitness of an individual is maximized by selecting the most profitable habitat. Spatio‐temporal gradients in temperature, turbidity, food availability and predation risk simulate the environment. We modeled predation as a function of temperature, the optical properties of the ambient water, the time allocation of feeding and the abundance of whiting (Merlangius merlangus). Growth and metabolic costs were assessed using a bioenergetic model. Model runs using real input data for the Scheldt estuary (Belgium, The Netherlands) and the southern North Sea show that estuarine residence results in fitter individuals through a considerable increase in survival probability of age‐0 fish. Young herring pay for their migration into safer estuarine water by foregoing growth opportunities at sea. We suggest that temperature and, in particular, the time lag between estuarine and seawater temperatures, acts as a basic cue for herring to navigate in the heterogeneous space between the offshore spawning grounds at sea and the oligohaline nursery zone in estuaries.     

Associations of fish with various types of littoral habitats in reservoirs

Fish associations with different types of littoral habitats were studied in four canyon‐shaped reservoirs in the Czech Republic in years 2010 and 2011 by gillnets. Two to three habitats per reservoir–beaches (former meadows), stump fields (former forest) and rubble slopes–were defined and sampled along the longitudinal axis of reservoirs. Effects of reservoir, habitat and locality (position along longitudinal axis) on fish biomass, abundance and species structure were tested for juvenile and adult fish separately. Hierarchical analysis of variance revealed that habitats differed significantly in fish biomass and abundance. Redundancy analysis showed that analysed environmental variables had significant influence on fish community structure. Most variability in community structure was explained by reservoir and then by combination of habitat and slope steepness. Locality position had the smallest influence on community structure. For both adult and juvenile fish total abundance and biomass, the most inhabited habitat was beaches; rubble slopes were the least inhabited. Habitat associations differed among species. Among adults, bream Abramis brama, white bream Blicca bjoerkna and roach Rutilus rutilus were associated with beaches and stump fields, whereas perch Perca fluviatilis, ruffe Gymnocephalus cernuus, asp Aspius aspius and pike Esox lucius were associated with rubble slopes. Bream, white bream, bleak Alburnus alburnus, roach, ruffe and pikeperch Sander lucioperca were associated with beaches among juveniles, whereas the only juvenile associated with rubble slopes was perch. We showed that most common species are associated with distinct habitats and also that utilisation of various littoral habitats differs in general.     

Relationships between macro‐epibenthic communities and fish on the shelf grounds of the western Mediterranean

• 1. The present study characterizes the macro‐epibenthic assemblages, and the relationships between demersal species and benthic habitats on the shelf trawl fishing grounds off the Balearic Islands (western Mediterranean).
• 2. The data used were collected during experimental bottom trawl surveys from 2002 to 2005. A total of 157 samples from 38–255 m depth were analysed.
• 3. Three macro‐epibenthic assemblages were identified in both the shallow (at 38–91 m) and deep shelf (90–255 m). Macroalgae bathymetric distribution was identified as the main factor explaining the segregation between shallow and deep shelf assemblages.
• 4. Two especially sensitive habitats were identified: maërl and crinoid beds; a third habitat was identified as Peyssonnelia beds, which represented the highest biomass on the whole shelf, with a similar species richness to the maërl beds. On the deep shelf, crinoid beds represented the highest biomass.
• 5. Habitat type had a significant effect on the distribution of demersal commercial species, most of them being more abundant in the two sensitive habitats mentioned and in the Peyssonnelia beds. Some species showed size‐specific habitat preferences.
• 6. Fisheries management in the area should take into account the resilience of these benthic habitats, and their importance from both ecological and sustainable fisheries management perspectives.

Copyright © 2008 John Wiley & Sons, Ltd.     

Defining critical habitat conditions for the conservation of three endemic and endangered cyprinids in a Mediterranean intermittent river before the onset of drought

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Growth, food conversion, maintenance and long-term survival of gilthead sea bream, Sparus auratus L., juveniles after abrupt transfer to low salinity

Juveniles of gilthead sea bream, Sparus auratus L., with individual weight 1.92 g, were reared under salinities of 8, 18, 28 and 38%o. The transfer to lower salinities (8-28%o) was abrupt. The results showed that better daily growth rates and food conversion efficiencies (FCE) when growing at 28%o gave the best performance. Statistically, salinity values above 28%o do not significantly affect daily growth rates and daily voluntary food intake. Maintenance requirement decreases linearly with increasing salinity. In particular, a l%o decrease of salinity is associated with a 0.014 (% body weight day^-1) increase of daily maintenance requirement. Mortality rates are high at salinities of 8 and 38%o (65% and 20% respectively) and minimal (1-3%) for fish reared under intermediate salinities (18-28%o). Finally, scope for growth, expressed as the minimum difference between food amount eaten and food attributed to growth, is better when the fish are kept at a salinity of 28%o. This means that most of the food amount eaten is attributed to growth and food wastage is minimal. These results confirm that gilthead sea bream fry show best performance when reared at a salinity of 28%o.     

基于栖息地指数的南海北部枪乌贼渔情预报模型构建

根据2009年~2014年南海捕捞信息网络获取的南海北部200 m等深线以内近海底拖网渔业数据,结合环境遥感数据,构建南海北部枪乌贼类(Uroteuthis sp.)栖息地指数(habitat suitability index,HSI)模型。选取海表水温(sea surface temperature,SST)、海面高度(sea surface height,SSH)和叶绿素a浓度(chlorophyll-a concentration,CHL)等环境因子,采用一元非线性回归建模,并分月份采用最小二乘法确定各环境因子的权重系数,从而建立南海北部枪乌贼类的栖息地指数综合模型。构建的模型能够有效解释渔场分布与环境要素之间的关系,并可从模型中推断各环境因子的最适范围和变化趋势;单位捕捞努力量渔获量(catch per unite effect,CPUE)高的渔场主要分布于HSI大于0.5的海域,其他HSI高的海域可能为潜在渔场。对不同因子权重系数的研究发现,叶绿素a浓度是影响渔场分布的重要因素。对模型的验证结果表明,其准确率达到75%以上。该研究表明,基于不同权重系数的HSI模型能够较好地预测南海北部枪乌贼渔场。     

Evidence of Morocco dentex (Dentex maroccanus) distribution in the NE Mediterranean and relationships with environmental factors determined by Generalized Additive Modelling

The seasonal distribution of Morocco dentex (Dentex maroccanus) was investigated in relation to ocean environmental conditions in the NE Mediterranean Sea. Data were collected during a 2‐yr period (1996–1997) of quasi‐synoptic seasonal sampling using demersal trawl surveys. The study revealed evidence for the existence of environmental relationships and temporal habitat associations of Morocco dentex. The sea‐bottom salinity, the water depth (through its interaction with bottom salinity) and the spatial location appeared to be key determinants of distribution. There was a strong consistency in the pattern and significance of the observed relationships across all seasons. The present results provided direct support for a preferential seasonal aggregation of Morocco dentex in specific geographic and bathymetric regions of the study area. In all four seasons, these favourable regions were found to be relatively stable and distinct, had the highest catch‐per‐unit‐effort index, and were located over shallower grounds (50–70 m) having bottom salinity around 39.1. The current findings also indicated that, throughout the year, the species was confined below the thermocline and avoided the deeper waters (>80 m). Morocco dentex ecological preferences for certain sea‐bottom salinities, water depth zones and hydrographic regimes were suggested to contribute to the processes governing differential settlement to preferred grounds.     

Acute Toxicity of Ammonia and Nitrite to Sea Bream,Sparus aurata (Linnaeus, 1758), in Relation to Salinity

Sea bream, Sparus aurata, is one of the most important fish species that is commonly cultured in the Mediterranean and the eastern coasts of the Atlantic Ocean. The life cycle of sea bream in its natural habitat passes through hyposaline and hypersaline lagoons. It is important to determine the tolerance of the fish to nitrogenous compounds for aquaculture at maximum stocking densities. In the present study, a series of acute experiments were performed to evaluate the effect of salinity on ammonia and nitrite toxicity to sea bream. The fish were exposed to different ammonia and nitrite concentrations according to the static renewal methodology at three different salinities (10, 20, and 30 ppt) and at a temperature of 20 C and a pH of 8.2. The toxic effect of total ammonia nitrogen (TAN) and nitrite nitrogen (NO₂‐N) decreased with increasing salinity levels (P < 0.001). Acute toxicity (96‐h lethal concentration 50 [LC₅₀]) values of TAN were determined to be 5.93, 11.72, and 19.38 mg/L at 10, 20, and 30 ppt salinity, respectively. The 96‐h LC₅₀ values of NO₂‐N were determined to be 370.80, 619.47, and 806.33 mg/L at 10, 20, and 30 ppt salinity, respectively. Results indicate that sea bream is less tolerant to ammonia but more tolerant to nitrite compared with some other fish species.     

Model of trawlable area using benthic terrain and oceanographic variables—Informing survey design and habitat maps in the Gulf of Alaska

Bottom trawl surveys provide fishery‐independent data on relative abundance and life history parameters for a wide range of marine taxa. Survey data are used to assess species distribution, biological interactions, and ecosystem structure and to manage marine resources. Not all bottom types or oceanographic conditions accommodate this survey method. We applied National Ocean Service hydrographic smooth sheets to evaluate physical attributes associated with habitat available to surveys. Random forests were used to evaluate the relative influence of benthic terrain and oceanographic predictors in determining accessibility to bottom trawl gear. We examined the marginal importance of each predictor, quantified the response gradient, and applied piecewise regression to determine threshold breakpoint values. Thresholds were used to develop predictive maps and distinguish untrawlable habitat at the scale of discrete towpaths and survey stations. Untrawlable habitat was associated with increased complexity in terrain, roughness, slope, surface curvature, substrate coarseness, current, and aspect. Maps of critical thresholds suggest different variables constrain the probability of a successful trawl in the nearshore, shelf, and continental slope. Overlay analysis of the model projection demonstrates the utility of archived smooth sheet data and identifies areas where higher resolution data might improve results. The model and maps produced in this analysis might be used to identify habitats available to and impacted by commercial trawl fisheries, inform the relative availability of various species and habitat types to bottom trawl surveys, evaluate bias in assessment indices and ecosystem metrics derived from survey data, and advance habitat‐specific biomass estimates.