Hydrographic,geomorphologic and fish assemblage relationships in coastal lagoons

In this study, 40 Atlanto-Mediterranean coastal lagoons were analyzed in order to evaluate the extent to which their ecological characteristics depend on hydrographic, trophic or geomorphologic features. Fish species richness increases with lagoon volume and the openness parameter, which characterizes the potential influence of the sea on general lagoon hydrology and is related to the total transversal area of the inlets, which connect the lagoon to the sea. On the other hand, the number of species decreases exponentially with the phosphate concentration in water. The fishing yield increases with the chlorophyll a concentration in the water column and exponentially with shoreline development. With respect to the fish assemblage composition, geomorphologic features alone explain 22% of the variance in the canonical analyses and an additional 75% when including the hydrographic and trophic characteristics of the lagoon, the latter on its own explaining only 3% of the observed differences.     

Fish assemblage in the Pearl River Estuary: Spatial‐seasonal variation,environmental influence and trends over the past three decades

The Pearl River Estuary is the largest estuary in South China and plays a considerable role in the local fisheries economy, yet little is known about the current state of fish assemblage in this ecosystem. To quantify spatial‐seasonal variations, environmental influences, and trends over the past three decades of the fish assemblage in the Pearl River Estuary, we sampled 11 sites seasonally from December 2013 to September 2016. Throughout the study, 285 species from 88 families and 195 genera were collected. There were obvious spatial and seasonal variations of the fish assemblage in terms of the dominant species, species richness, and composition of ecological types. Mouth distance, NH₄⁺ N, chlorophyll‐a, flow, DO, salinity and water transparency were the main variables influencing the spatial‐temporal dynamic of fishes within the estuarine systems. Compared with the record of 330 species in the 1980s, the number of fish species in the Pearl River Estuary has declined by 45 fish species. The Jaccard's similarity of fish composition between the historical investigation (the 1980's) and the present investigation (2013–2016) was 0.62, with 95 species undiscovered and 50 species increased in the present study compared to the 1980s, indicating the assemblage structure has obviously changed. However, in term of ecological guilds, there was no significant difference in the composition of all the selected ecological traits between these two periods. Anthropogenic activities including overfishing, introducing alien fish, dam construction and pollution were considered the main disturbance on fish composition over the past three decades. We conclude that there existed pronounced spatiotemporal changes of fish assemblages, which arises from the compounding effects of environmental factors and anthropogenic activities. These findings are beneficial to understanding and developing suitable conservation strategies for the management and protection of fish resources in the Pearl River Estuary.     

The fish assemblage of the intertidal salt marsh creeks in North Bull Island, Dublin Bay: seasonal and tidal changes in composition, distribution and abundance

An intertidal salt marsh fish assemblage inhabiting two creeks on North Bull Island, Dublin Bay was sampled monthly from June 2000 until May 2002. Water temperature and salinity were recorded in situ and samples were also taken for Suspended Particulate Matter (SPM) and Chlorophyll a. All fish caught were weighed and measured and classified into functional guilds. A total of 6,549 individuals comprising 10 fish species from 10 families were recorded within the two creeks. The community was dominated by a few species, a feature common to other estuarine fish populations. Of the 10 species found, the common goby, Pomatoschistus microps, the 3-spined stickleback, Gasterosteus aculeatus, the thick-lipped grey mullet, Chelon labrosus and the flounder, Platichthys flesus contributed 98.4% of all fish sampled. The fish population of the channels at Bull Island, Dublin, was dominated by the resident gobies (true estuarine resident species), but also hosted juveniles of species such as the bass, Dicentrarchus labrax (marine juvenile migrant species). In turn, the nekton populations were dominated by the brown shrimp, Crangon crangon and the fairy shrimp, Palaemonetes varians especially in winter when fewer fish (numbers of species and abundance) were found. Multivariate analysis of fish diversity and abundance revealed a strong seasonal pattern but there was little evidence of difference between creeks, nor of tidal (spring/neap) effects. The estuarine fish using the intertidal marsh creeks have been little studied in Europe yet they play a major role with the decapods in these habitats. This role needs to be quantified for a proper understanding of the system’s function.     

Changes in the composition of British butterfly assemblages over two decades

Changes in the abundance and distribution of individual species have been widely documented in Britain and other countries in recent decades, but little has been done to determine changes in community composition over broad geographic areas. Here, we studied species turnover in 51 butterfly assemblages in Britain since 1976, examining extinction and colonisation events together with variation in the abundances of the species. We showed that the species turnover that occurred over 20 years in Britain was associated with colonisation and extinction events and also with variability in the abundance of the species. These changes in community composition differed according to the habitat requirements of the species and their previous distributions, being more evident for habitat specialists and for southerly distributed species. Colonising species often became abundant components of the communities they joined, although this was more evident for generalist than for specialist species. The abundance of species following their arrival, increased with time since colonisation. Species turnover associated with southerly species expanding northwards is consistent with being a response to climate change. The results suggest that climate- and habitat-driven changes in the identity and abundance of species within communities are widespread, and probably ubiquitous. Similar changes are likely to be occurring in other groups of organisms that are similarly undertaking major range shifts associated with climate change.     

Spatial and seasonal dynamics of fish assemblage along river Soan,Pakistan and its relationship with environmental conditions

This study aims to discuss the seasonal and spatial dynamics of fish assemblage of River Soan in relation with environmental changes. Survey was conducted during pre monsoon and post monsoon seasons in 2008. Physico chemical and biological samplings were carried out at 26 sites which were selected along the whole stretch of the river. High concentration of total phosphorous and conductivity, low pH and dissolved oxygen were measured at urban part of midstream zone whereas high concentration of total nitrogen was measured at downstream zone. A total of 22 species were collected during the survey among which Barilius pakistanicus, Puntius ticto, Crossocheilus diplochilus and Labeo dero were distributed throughout the river stretch. Maximum fish diversity was recorded at suburban part of midstream while its urban part was appeared to be the most species poor part of the Soan River. Herbivore individuals constituted the dominant trophic group of fish assemblage. Significant seasonal and spatial changes in fish assemblage were determined at river downstream. Upstream- downstream differences in fish assemblage were more pronounced during pre monsoon and seem to be related to thermal gradient and hydrological changes. Seasonal variations in fish assemblage were significant only at downstream zone and were influenced by velocity, floodplains and migration patterns in fish assemblage. Understanding of spatial and seasonal trends in fish assemblage in relation with their environment is of great importance for the management and conservation of fish assemblage. Findings of this study will be helpful in future attempts to restore and conserve the aquatic assemblages of Himalayan streams.     

Phytogeography of Lusitanian Macaronesia: biogeographic affinities in species richness and assemblage composition

Analysis of biogeographic affinities is a key tool to establish and improve the resolution of hierarchical biogeographic systems. We describe patterns of species richness of the marine macroalgal flora across Lusitanian Macaronesia (Azores, Madeira, the Salvage Islands and the Canary Islands), and test (i) whether such differences are related to differences in proximity to the nearest continental shore and size among islands. We also explore biogeographic affinities in the composition of macroalgal assemblages (= presence/absence of each taxon in multivariate datasets) to determine (ii) whether each archipelago is a biogeographic unit within this ecoregion and (iii) whether patterns in assemblage composition are related to proximity (i.e. distances) among islands. Presence/absence matrices were created to test and visualize multivariate affinities among archipelagos. A total of 872 taxa were compiled. Species richness peaked at the Canary Islands and decreased towards the Azores; the pattern matched a progressive increase in distance from the nearest continental shores, matching the classical island biogeography theory. Intra-archipelago differences in species richness were largely related to variations in island size. Biogeographic similarities among archipelagos were hierarchically structured. Madeira and the Salvage Islands constituted one biogeographic unit. Floras from the Azores, Madeira and the Salvage Islands were barely separable from each other, but were different from those at the Canary Islands. Such biogeographic similarities among islands were negatively correlated with the geographical separation (i.e. distances) among them. Proximity to nearby continental shores, in conjunction with large- and meso-scale oceanographic patterns, seems to interact to create patterns in richness and composition of algal assemblages across Lusitanian Macaronesia.     

Convergent signs of degradation in both the capacity and the quality of an essential fish habitat: state of the Seine estuary (France) flatfish nurseries

The Bay of Seine is a potentially important nursery ground, especially for flatfish. This area, however, is also strongly anthropogenically influenced. A composite approach was chosen to compare the flatfish nursery function of the Seine estuary with other coastal and estuarine areas and to determine the impact of anthropogenic disturbances. It emerges that alteration of the nursery function in the Seine estuary is related to the loss of nursery habitat and to a lower quality of the residual surfaces. These observations stressed the importance of habitat destruction and decreased quality of remaining habitat for fish stocks renewal.     

Variation in fish density,assemblage composition and relative rates of predation among mangrove,seagrass and coral reef habitats

We tested the hypothesis for several Caribbean reef fish species that there is no difference in nursery function among mangrove, seagrass and shallow reef habitat as measured by: (a) patterns of juvenile and adult density, (b) assemblage composition, and (c) relative predation rates. Results indicated that although some mangrove and seagrass sites showed characteristics of nursery habitats, this pattern was weak. While almost half of our mangrove and seagrass sites appeared to hold higher proportions of juvenile fish (all species pooled) than did reef sites, this pattern was significant in only two cases. In addition, only four of the six most abundant and commercially important species (Haemulon flavolineatum, Haemulon sciurus, Lutjanus apodus, Lutjanus mahogoni, Scarus iserti, and Sparisoma aurofrenatum) showed patterns of higher proportions of juvenile fish in mangrove and/or seagrass habitat(s) relative to coral reefs, and were limited to four of nine sites. Faunal similarity between reef and either mangrove or seagrass habitats was low, suggesting little, if any exchange between them. Finally, although relative risk of predation was lower in mangrove/seagrass than in reef habitats, variance in rates was substantial suggesting that not all mangrove/seagrass habitats function equivalently. Specifically, relative risk varied between morning and afternoon, and between sites of similar habitat, yet varied little, in some cases, between habitats (mangrove/seagrass vs. coral reefs). Consequently, our results caution against generalizations that all mangrove and seagrass habitats have nursery function.     

Otters and fish farms in the Sado estuary: ecological and socio-economic basis of a conflict

The degree of conflict between otter conservation and fish farming was assessed at Sado estuary (SW Portugal), using ecological (otter visiting rates to fish farms and consumption of commercial fish) and socio-economic (past and current instruments and policies addressing the conflict and a social impact assessment, including a discourse analysis of relevant stakeholders) parameters. The study concerned 14 fish farms producing Sparus aurata, Dicentrarchus labrax, Solea senegalensis and Solea solea. Results indicate high visiting rates in most fish farms (average: 76%), although in only 29%, species stocked were the most consumed prey. Other marine species and freshwater prey were the basis of otter diet in the remaining fish farms. The conflict is quite consensual among most fish farmers, and the results indicate that the perceived conflict by fish farmers has an ecological basis, although there are large gaps between effective and perceived predation. No specific instruments exist in Portugal to address the conflict, but some not specifically targeted can have an effect (e.g. species protection legislation and aquaculture licensing), although with limitations to effectively contribute to its mitigation (e.g. lack of enforcement and supervision). Formulating and assessing solutions is the following step, using a participatory approach to the development and evaluation of mitigation/compensation strategies, capable of providing an effective reconciliation of the conflict.

The upper reached ichthyofauna of the Tietê River, São Paulo, Brazil: aspects of their diversity and conservation

Tietê River is one of the main rivers in the State of São Paulo, Brazil. It runs across this state from east to west for 1136 km. The upper reach of the Tietê River is located in the metropolitan region of the city of São Paulo where approximately 60% of the original Atlantic Forest remnants has been converted into rural and urban areas. Ichthyofauna of the upper reaches of the rivers is usually characterized by a high level of endemism, small fish with restricted geographic distribution. A qualitative survey of two main tributaries, Paraitinga and Biritiba Mirim Rivers, and a stretch of the Tietê River was carried out in order to ascertain their fish community composition, compare the former fish data collected in the same area and establish biodiversity conservation research programs. The fish fauna in the three riverine systems comprises 5 orders, 9 families, 20 genus and 28 species. One species, Glandulocauda melanogenys, out of sixteen regarded as strictly endemic to the upper reaches of the Tietê River according to previous data was found among the sampled collections. No established alien species were found despite their presence in the upstream reservoir of the Tietê Rivers. Human disturbances and their impacts on fish diversity are discussed, including their relation to the ecotone habitats.     

黄河干流鱼类群落特征及其历史变化

为了解黄河干流鱼类群落现状及其历史变化,于2008年春季(5-6月)和秋季(9-11月)开展了黄河干流鱼类调查。共记录到鱼类54种,隶属于7目13科43属,其中该流域特有种4种。种类组成以鲤形目为主,占总数的68.5%。上游物种少,群落较为简单,中游和下游物种丰富,群落较为复杂并且较相似,种数自上游至下游逐渐增加。黄河鱼类在洄游、摄食、繁殖及栖息习性等方面呈现多样化特征。调查河段渔获物组成虽存在差异,但都以黄颡鱼属(Pelteobagrus spp.)、鲇(Silurus asotus)、鲫(Carassius auratus)以及鮈亚科等小型鱼类为主,小型化现象明显。对比历史资料分析显示,黄河鱼类物种多样性和资源量均呈明显下降趋势,特有种鱼类退化尤为显著,推测水资源过度开发、大量水工建筑、水体污染以及不合理利用等人为因素是导致变化的主要原因。     

Diversity,composition, and structure of tropical dry forests in Central America

Tropical dry forests have been reduced to less than 0.1% of their original expanse on the Pacific side of Central America and are considered by some to be the most endangered ecosystem in the lowland tropics. Plots 1000 m² were established in seven tropical dry forests in Costa Rica and Nicaragua in order to compare levels of species richness to other Neotropical dry forest sites and to identify environmental variables associated with species richness and abundance. A total of 204 species and 1484 individuals 2.5 cm were encountered. Santa Rosa National Park was the richest site with the highest family (33), genera (69), and species (75) diversity of all sites. Species richness and forest structure were significantly different between sites. Fabaceae was the dominant tree and shrub family at most sites, but no species was repeatably dominant based on number of stems in all fragments of tropical dry forest. Central American dry forests had similar species richness when compared to other Neotropical forests. There was no correlation between forest cover within reserves, or precipitation and plant species richness. There was a significant correlation between anthropogenic disturbance (intensity and frequency of fire, wood collection, grazing) and total species richness, tree and shrub species richness, and liana abundance. These results suggest controlling levels on anthropogenic disturbance within reserves should be a high priority for resource managers in Central America. Further research in forest fragments which examine individual and a combination of disturbance agents would help clarify the importance of anthropogenic disturbance on species richness and abundance.     

Identifying the scales of variability in stream macroinvertebrate abundance, functional composition and assemblage structure

1. Many natural ecosystems are heterogeneous at scales ranging from microhabitats to landscapes. Running waters are no exception in this regard, and their environmental heterogeneity is reflected in the distribution and abundance of stream organisms across multiple spatial scales. 2. We studied patchiness in benthic macroinvertebrate abundance and functional feeding group (FFG) composition at three spatial scales in a boreal river system. Our sampling design incorporated a set of fully nested scales, with three tributaries, two stream sections (orders) within each tributary, three riffles within each section and ten benthic samples in each riffle. 3. According to nested anova s, most of the variation in total macroinvertebrate abundance, abundances of FFGs, and number of taxa was accounted for by the among‐riffle and among‐sample scales. Such small‐scale variability reflected similar patterns of variation in in‐stream variables (moss cover, particle size, current velocity and depth). Scraper abundance, however, varied most at the scale of stream sections, probably mirroring variation in canopy cover. 4. Tributaries and stream sections within tributaries differed significantly in the structure and FFG composition of the macroinvertebrate assemblages. Furthermore, riffles in headwater (second order) sections were more variable than those in higher order (third order) sections. 5. Stream biomonitoring programs should consider this kind of scale‐dependent variability in assemblage characteristics because: (i) small‐scale variability in abundance suggests that a few replicate samples are not enough to capture macroinvertebrate assemblage variability present at a site, and (ii) riffles from the same stream may support widely differing benthic assemblages.     

Littoral zone fish communities of two Florida lakes and a comparison with Michigan lakes

Synopsis The abundance and habitat distribution of littoral zone fishes in two small southern Florida lakes were quantified by underwater censuses. The bluegill (Lepomis macrochirus) and large-mouth bass (Micropterus salmoides) accounted for 75–80% of community biomass in both lakes; important coexisting species were predominantly benthic feeders in Lake Sirena and planktivores in Lake Annie. All species were largely confined to areas of macrovegetation which extended to a depth of 4 m in Lake Annie but only to 1.2 m in Lake Sirena. The differences in community structure were related to differences in habitat and also variation in water levels and benthic production.A comparison of community composition with that of small Michigan lakes indicated that similar numbers of species coexist in the littoral zones, despite a three-fold difference in the size of regional species pools. The majority of families and about 50% of the species were common to lakes in both regions; in addition a number of ecological analogues were noted. A major difference was that the small inshore species were members of the Cyprinodontiformes in Florida and Cyprinidae in Michigan. Together the largemouth bass and bluegill comprise similar community proportions in the two regions as do other major feeding groups. Lakes in the two regions that are similar in amount and distribution of vegetation exhibit greater similarity in fish communities than those within regions that differ in littoral vegetation.     

Forest structure and tree species composition of the understory of two central Amazonian várzea forests of contrasting flood heights

We investigated species composition, distribution, and forest structure of understory trees (≥1 m height, <10 cm diameter at breast height) in two late-successional várzea forests subject to contrasting levels of inundation within the Mamirauá Sustainable Development Reserve, western Brazilian Amazon, and compared it with the overstory flora at the same study sites. In total, 1486 individuals and 116 woody species were recorded on an area totaling 3140 m². Individual densities and tree species richness were considerably higher in the high várzea than in the low várzea, which suggests that the heights and durations of the annual inundations are the main factor limiting species regeneration. In addition, approximately one third of the recorded species with densities ≥8 individuals showed regular or random spatial distribution patterns, which suggests that floodwaters act on dispersal strategies and species establishment.Independent of the forest type, floristic similarity between the understory and the overstory amounted to approximately 35%, and to approximately 10% when compared to other understory inventories in Amazonian várzea. Although the inventoried area of the understory amounted to only 16% of that of the overstory, species richness accounted for approximately 52-56% of that of the overstory. The results indicate that the understory flora of várzea forests is distinct and that it significantly increases local tree species richness. The understory flora of várzea forests therefore should be addressed in floristic inventories that provide the basis for regional and/or basin-wide estimations of tree diversity.     

Regional and longitudinal patterns of fish community structure in the Seine River basin, France

The fish communities of 371 sites from 4 natural regions of the Seine River basin were studied. The sites were located from small to medium size rivers (catchment area : 5 to 3895 km²). We examined the differences between local communities according to river size (estimated by catchment area) and region. In the Seine River basin, fish communities follow a general organisation rule: total species richness increases with river size and importance of limnophilic species versus rheophilic ones increases from upstream to downstream. However, fish communities show differences of total species richness, species richness of reproductive groups and species composition between the four natural regions of the basin. Particularly, river size and regional organisation of environmental factors interact on species composition of communities and several regional patterns of longitudinal changes of fish communities are identified. The origin and range of regional differences of fish communities are discussed according to historical and environmental factors.     

The fish assemblage on a coralligenous shallow shelf off the Mediterranean coast of northern Israel

The fish assemblage on the shallow coralligenous shelf (16-30m depth) off Haifa, Israel was sampled using trammel nets throughout a period of 1 year. Complementary data were obtained via underwater censuses of fish on an artificial reef established later in the sampling area. Fortythree species of fish were sampled by trammel nets, 79% of which were observed also during the underwater censuses. Although fish of Red Sea origin constituted only 11.6% of the species composition in the net samples, they contributed 46.2% of the fish abundance and 40.6% of the biomass in these samples. This was supported by the finding that species of Red Sea origin contributed 64% of the abundance of large fish counted on the artificial reef. Siganus luridas, S. rivulatus and Sargocentron rubrum are the main contributors in number and biomass among fish of Red Sea origin. It is suggested that the biogenic rocky bottom of this area contains several components which are similar to biogenic habitats favoured by these benthic species in the Red Sea; this may explain the high abundance of these species in the studied area.     

长江口附近海域春季浮游硅藻的种类组成和生态分布

2002年春季,在长江口附近海域典型赤潮高发区28个大面站位采集了53个样品,从中共鉴定出隶属于31个硅藻属的80个种和变种;其中种类多样性较高的属为圆筛藻属(Coscinodiscus),有17个种,斜纹藻属(Pleurosigma),有8个种和变种;数量上较优势的种为柔弱拟菱形藻(pseudo-nitzschia delicatissma),为3．48×10^3cells·L-1,占28．54％;具槽直链藻(Melosira sulcata),为1．43×10^3cells·L-1,占16．98％;尖刺拟菱形藻(Pseudo-nitzschia pungens),为0．71×10^3cells·L-1,占9．85％．它们在大部分站位中都有出现;柔弱拟菱形藻和尖刺拟菱形藻的高细胞密度区主要出现在1230E断面的站位,而具槽直链藻则主要出现在长江口的31～32°N断面的站位．浮游硅藻总细胞丰度变化于0．43×10^3～23．3×10^3cells·L-1,平均4．61×10^3cells·L-1;在123°E、30．5°N的DDl5站位,无论表层还是中层,浮游硅藻总细胞丰度均最高(表层,1．85×10^4cells·L-1;中层,2．33×10^4cells·L-1)．从水平分布看,浮游硅藻呈不均匀分布态势,从垂直分布看,大部分站位的表层浮游硅藻丰度高于中层．     

泸沽湖及其附近竹地海湿地越冬水鸟群落组成及历史变化分析

泸沽湖是中国西南重要的水鸟越冬地和旅游风景区,开展泸沽湖越冬水鸟群落组成现状调查并进行历史变化分析,对指导泸沽湖水鸟及其栖息地保护和管理具有重要意义。2013年10月至2014年2月(12月除外),逐月对泸沽湖全湖及其西北方向的竹地海湿地(距离泸沽湖约500 m,面积约0.4 km2)越冬水鸟进行调查。泸沽湖共记录到水鸟27种,观察的最大个体总数约为22 600只,符合国际重要湿地标准。泸沽湖越冬水鸟群落的主要优势物种为骨顶鸡(Fulica atra),其最大观察数约为10 300只。竹地海湿地共记录到水鸟16种,观察到的最大个体总数约为3 600只,其中赤麻鸭(Tadorna ferruginea)约为2 700只;鉴于竹地海湿地亦为水鸟聚集的栖息地,建议将其划入泸沽湖自然保护区加以保护。对比1992年的调查数据,发现泸沽湖及其附近竹地海湿地越冬水鸟的物种丰富度(species richness)可能有所下降,由原来的33种下降到现在的30种,但个体总数量相对稳定。多种涉禽和喜浅水活动的钻水鸭类(dabbling ducks)消失,可能与湖岸区旅游活动的持续进行有关;泸沽湖曾经的主要优势物种赤嘴潜鸭(Netta rufina)种群数量大幅下降,暗示泸沽湖生态系统可能已发生变化。泸沽湖旅游业进一步发展的同时,保护好现存的浅水栖息地将是泸沽湖水鸟多样性不再继续下降的关键。