Partitioning of the feeding niche along spatial,seasonal and size dimensions by the fish community in a tropical Bay in Southeastern Brazil

Feeding guilds and spatial, seasonal and ontogenetic changes in the diets of 24 fish species in a tropical bay in Southeastern Brazil were examined. The hypotheses tested were that groups of species form specific trophic guilds and that the feeding partitioning differs along the niche dimensions. Five trophic guilds (Polychaeta, Copepoda, Teleostei, Teleostei/Crustacea and Polychaeta/Crustacea) and two species with specialised feeding, one teleost (Aspistor luniscutis) and one bivalvia (Sphoeroides testudineus), were found. Polychaeta was the most important resource for nine fish species, followed by Copepoda (6 spp.), Teleostei (5 spp.) and Caprelidae Amphipoda (3 spp.). Polychaeta was the most used resource for species in the inner bay zone, and Crustaceans in the outer bay zone. We detected a predominance of Polychaeta between the spring and autumn, whereas crustaceans were consumed at a greater rate in the winter. The most conspicuous changes in diet occurred along the spatial and seasonal dimensions, rather than the size dimensions. The hypotheses tested were accepted. Identifying and incorporating information about the bay food web is a first step towards developing management strategies that are sensitive to this particular ecosystem.     

渤、黄、东海高营养层次重要生物资源种类的营养级研究

利用2000年和2001年2次大面调查所收集的11970个胃含物样品分析结果,计算了黄海和东海生态系统高营养层次35个重要生物资源种类的营养级,同时,结合对渤海和黄海39个种类营养级历史数据的修正,讨论研究了我国海洋高营养层次生物资源种类营养级的研究策略和计算方法。主要研究结果为：(1)渤海重要生物资源种类营养级的变化范围为3．12～4．9,黄海为3．2～4．9,东海为3．29～4．55。近年来各海域高营养层次的营养级呈下降趋势,如渤海从1959年的4．1下降到1998～1999年的3．4,黄海从1985～1986年的3．7下降到2000～2001年的3．4;(2)高营养层次营养级波动主要是由于群落种类组成变化及单种类营养级年间波动引起的,而单种类营养级年间波动又直接与群体个体变小以及摄食食物的低营养层次化有关。因此,高营养层次的营养级变化是认识海洋生态系统生物生产动态的重要指标,需要对其进行长期和系统的监测;(3)建议在今后的研究中,根据简化食物网的概念,对占生物量绝对多数的重要生物资源种类的营养级进行重点研究并采用国际通用的标准划分计算营养级。     

Reduction of flatfish habitat as a consequence of the proliferation of an invasive mollusc

Coastal bays provide habitats for juveniles and adults of many marine species. Mont Saint-Michel Bay (MSMB, France) hosts a highly diversified fish community and constitutes one of the most important nursery grounds for many commercially exploited marine species, such as sea bass, flatfish, clupeids and rays in the English Channel. Besides, MSMB also suffers from the massive invasion of an exotic mollusc, the American slipper-limpet (Crepidula fornicata, L.). This species arrived four decades ago and now represents the main filter-feeder biomass in the bay (150 Mt), an order of magnitude larger than local farmed and natural shellfishes. Recent analyses underlined the impact of this small gastropod on the trophic structure of this bay and its negative influence on juvenile sole densities in the nursery grounds. The present study uses a geostatistical approach to explore the effect of the extension of the slipper-limpet on flatfish (common sole Solea solea, L.; plaice Pleuronectes platessa, L.; brill Scophthalmus rhombus, L. and flounder Platichthys flesus, L.) spatial distribution. Data collected during survey of the MSMB at the end of the 1970s and three decades later have been used to build interpolated maps of (1) slipper-limpet and (2) flatfish spatial distributions. Slipper-limpets were concentrated in a small area, in the western part of the MSMB, in the 1970s while today they occupy half of the bay. This rapid proliferation led to the decrease of available surface for flatfishes, which previously occupied the whole bay and are now restricted to its eastern part. The present study highlighted that the negative influence on fish habitat in MSMB is apparently more related to changes in the substratum than to trophic interactions. This invasion has possible consequences on flatfish population renewal at a large scale and may also damage other benthic or demersal species, such as rays.     

基于碳氮稳定同位素技术的小清河口邻近海域底栖食物网结构研究

为了掌握小清河口邻近海域底栖食物网结构特征,于2020年10月在小清河口邻近海域采集沉积物有机质、悬浮颗粒有机物、浮游动物和浮游植物4种潜在食源及35种生物样本,应用碳氮稳定同位素技术以及贝叶斯混合模型(MixSIAR)分析了小清河口邻近海域底栖食物网结构和营养关系.结果显示,潜在食源的δ13C值范围为-25.56‰～...     

应用稳定同位素技术研究江苏近海食物网营养结构的季节性变化

本研究基于稳定同位素技术对江苏近海春、夏、秋季采集的不同生物类群(鱼类、甲壳类、头足类和底栖动物等)进行稳定同位素的分析,利用SIBER模型计算不同季节消费者的营养生态位,并计算出6种营养结构的量化指标.结果表明,3个季节的δ13C值、δ15N值均差异不显著(p>0.05).春季δ13C值范围为?24.47‰～?14....     

厦门东海域鱼类食物网研究

本文分析了厦门东海域58种鱼类的营养关系.根据对它们的食性分析,并依其食料生物的生态类群,将厦门东海域的鱼类食性类型分为:浮游生物食性、底栖生物食性、游泳动物食性、浮游生物和底栖生物、底栖生物和游泳动物食性等5种.该海域鱼类的营养级可分为4级:杂食性鱼类、低级肉食性鱼类、中级肉食性鱼类和高级肉食性鱼类,其中低级肉食性鱼类占优势,为63.79%.本文还分析了厦门东海域鱼类的食物网及其能量流动途径,并提出合理利用和保护厦门东海域鱼类资源的建议.     

Macrobenthos of Kakinada Bay in the Godavari delta, East coast of India: comparing decadal changes

A one-year study (1995–1996) on the macrobenthos over a spread of (37) hydrographically differing GPS-fixed sites in Kakinada Bay (mean salinity 27.16±0.4) and adjacent mangrove channels (14.78±0.55) in the Godavari delta, one of India's largest estuarine systems, revealed a great preponderance of benthic life. There were 11 diverse taxa represented by 95 species collected through several (303) grab and dredge hauls. Based on Bray-Curtis similarity through hierarchical clustering implemented in PRIMER, it was possible to distinguish the benthos into four assemblages each of which represented sites in the Central and North bay (Paphia textrix – Typhlocarcinus sp. Assemblage), South-East bay (Protankyra similis – Paphia malabarica Assemblage), Mangrove Outlets (Cerithidea cingulata Assemblage) and Mangrove channels (Diopatra neapolitana Assemblage). Benthos densities (mean nos. dredge haul⁻¹) were highest (299 individuals) at sites close to mangrove outlets. Species diversity (Margalef, d; Shannon-Wiener, H′) was low in general (d 1.244 to 2.251 and H′ 0.038 to 1.502). Sediments were mostly clayey-silt in nature except in southeast bay where they are silt-sand. Organic matter (mean) was at or near 1.3%. The observations have revealed marked changes in benthic community structure relative to an earlier investigation held in 1958–1963 in this area. Over the years, species such as Turritella duplicata, Tonna dolium and Placuna placenta found in considerable numbers previously have dwindled. Anomia, Bursa and Atrina and echinoderms, Astropecten indica, Echinodiscus auritus and Temnopleurus toreumaticus and the brachiopod, Lingula sp. of common occurrence in early 60s are absent altogether attributable to long-term natural trends during the intervening years and/or events accompanying human impingement (e.g. industrial and urban growth, port expansion measures, aquaculture, mangrove denudation etc.). Despite such large-scale alterations in benthos community structure, there were no significant changes in “biodiversity” measured through Average Taxonomic Distinctness (AvTD) and Variation in Taxonomic Distinctness (VarTD). The investigation revealed that AvTD (Δ⁺) and VarTD (Λ⁺) for previous years and the present study remained well within the 95% confidence funnel implying taxonomic stability. It was found that species, which had replaced the earlier forms, were drawn from comparable (Linnean) hierarchy i.e. same phylum/class.     

Interactions between a natural food web,shellfish farming and exotic species: The case of the Bay of Mont Saint Michel (France)

To ensure sustainable uses of the coastal zone, an integrated ecosystemic approach and ecosystem models are required to frame ecological processes and evaluate environmental impacts. Here, a mass-balance trophic (Ecopath) model of the Mont Saint Michel Bay (MSMB) was developed, to analyze the bay's functioning as an ecosystem. This bay, intensively exploited by fishing and for shellfish farming, is also suffering from the proliferation of the gastropod Crepidula fornicata, an exotic species.     

Nematode community dynamics over an annual production cycle in the central North Sea

Nematode species composition, trophic structure and body size distributions were followed over an annual production cycle in the central North Sea; to test responses to temporally changing food quality and quantity in the sediment. Changes in the phytoplankton concentration in the water column were quantitatively reflected in the concentration of chlorophyll a and breakdown products in the sediment, with higher concentrations in spring and autumn following blooms, and lower concentrations in summer and winter. The taxonomic and trophic structure of nematode communities differed significantly among stations over relatively short distances, potentially masking some of the temporal dynamics. Spatio-temporal differences in nematode species composition were linked to changes in the quality and quantity of organic material reaching the seabed, reflecting a species-specific response to the nutritional quality of sedimenting organic material and the biochemical changes in the sediment associated with its decomposition. The size distributions of selected nematode species indicated that most species bred continuously throughout the sampling period, although one species, the epigrowth feeder Spilophorella paradoxa, had periods of increased growth following the deposition of the spring phytoplankton bloom. There was no consistent temporal relationship between the trophic composition of nematode communities and spring chlorophyll a or carbon sedimentation, most likely a result of the trophic plasticity of most feeding types and the capacity of the community to use both freshly sedimented material as well as the subsequent breakdown products and refractory organic matter. Community metrics implied that there were small responses to the seasonal production cycle, but these belied strong responses of a few species with life histories that allowed them to track the availability of suitable food resources.     

Spatial and temporal characteristics of trophic structure of the southern Huanghai Sea fish communities

The spatial and temporal characteristics of trophic structure of fish communities in the southern Huanghai Sea were examined based on the data sampled from bottom trawl surveys conducted during the autumn of 2000 and the spring of 2001. Hierarchical agglomerative cluster method and bootstrap randomization were used to identify significant trophic groups for each fish assemblage in the southern Huanghai Sea. A total of six major trophic groups were identified within this system, which classified predators based upon location in the water column or prey size （ i. e. , benthic to pelagic predators or fish to small invertebrate prey predators）. The similarity level used to identify significant trophic groups in each assemblage ranged from 24% to 34%. Although planktivores were the dominant trophic group in each assemblage （60% - 79% ）, there were spatial and temporal variations in the trophic structure, which reflected the differences in the abundance and availability of dominant preys. Simplified food webs were constructed to evaluate the most important trophic relationships between the dominant prey taxa and the fishes in each assemblage within this system. Although there were some differences in the key prey species among different food webs, pelagic prey items （mainly euphausiids and copepods） represent the most important energetic link between primary producers and higher trophic level predators. The trophic level for most fishes was between 3 and d, and the weighted mean trophic level for each assemblage ranged from 3.3 to 3.4. Compared with previous study in the mid-1980s, there was an obvious downward trend in the trophic level for most fish species, which resulted mainly from the fluctuation in key prey species in the Huanghai Sea. The decrease in the importance of Japanese anchovy seems to be offset by other abundant prey species such as Euphausia pacifica and copepods （ mainly Calanus sinicus ） .     

九龙江口外浯屿海域底栖生物种类组成与数量分布

本文根据１９９５年的调查，报道了九龙江口外浯屿海域底栖生物的种类组成与数量分布。结果表明，本区底栖生物种类较丰富，组成以多毛类，甲动物，软体动物和棘皮动物为主。底栖生物数量较大，平均栖息密度为３００个／ｍ＾２，平均生物量为３１．０３ｇ／ｍ＾３，数量分布较不均匀。．     

Does the Port 2000 harbour construction have an effect on the Seine estuary suprabenthic community?

Using a Before/During/After protocol, the effects of Port 2000 (the Le Havre harbour extension) on the suprabenthic communities in the Northern Channel of the Seine estuary (English Channel) were examined from March 2001 to March 2009. Since the beginning of Port 2000 construction in 2002, there have been several changes in the hydrological and sedimentary characteristics in the North Channel, including changes in current velocity, bottoms salinity and sand accumulation, as well as in the benthic communities themselves, moving from mud to medium and coarse sand communities. For the suprabenthos, changes were moderate, corresponding to an increase in species richness in the upper-part of the North Channel and a decrease in species density in the dominant mysids species (i.e., mainly Mesopodospsis slabberi) over time. Due to hydrological changes since the beginning of the Port 2000 project (several years of low freshwater input) it has been difficult to attribute the biological changes to Port 2000 construction only. In the future, the results obtained for the suprabenthos will have to be compared to those obtained for the macrobenthos. Similarly, since the suprabenthos is known to play an important role in the estuarine trophic chain, it will also be essential to estimate the fish distribution in the North Channel and to examine their stomach contents to evaluate the probable changes since the Port 2000 project began.     

渤海蓝点马鲛食物链结构的研究

从60年代起,我国开始进行鱼类食性的研究(杨纪明、郑严,1962;杨纪明、林景祺，1966),并且开始以食性分析的方法,对特定海区内的鱼类食物关系进行研究(邓景耀等,1986;张其永等,1981),这为海洋食物链研究提供了初步资料。但至今尚未见有单种鱼食物链结构的研究报道。 蓝点马鮫 Scomberomorus niphonius (Cuvier et Valenciennes)为暖水性、洄游性、中上层鱼类。通常每年6月进入渤海产卵,11月前后离开渤海,向深海做越冬洄游(韦晟,1980)。蓝点马鲛作为渤海的重要经济鱼类之一,近些年来资源量一直保持相对稳定(韦晟,1982;朱德山、韦晟,1983)。进行蓝点马鲛的食物链研究,一方面有助于进行蓝点马鮫资源的预测、增殖及管理,另一方面对阐明渤海生态系统中的能量转换也具有一定意义。本文试图对蓝点马鲛食物链结构问题进行讨论。     

长江口及邻近水域的生物多样性变化趋势分析

从长江口及邻近水域的生物多样性变化及导致生物多样性变化的相关环境因子来剖析长江口及邻近水域的生态环境变化趋势。长江口及邻近水域的生物多样性比较丰富。近20a来在人类活动影响下,长江河口区和冲淡水区浮游生物和底栖生物的物种大幅减少：优势浮游生物的生物量增加,部分种类异常增殖发生赤潮,底栖生物生物量明显减少;群落结构趋向简单,表现为单种优势,生物多样性下降。影响长江口及邻近水域生物多样性的原因包括自然因素和人为因素,近20a来生物多样性的降低主要归咎于人类的开发活动,不合理排污导致的富营养化对浮游生物的多样性丧失起重要作用,水利工程建设及滩涂围垦使海洋生物栖息地片段化,单调化,加速了生物多样性的降低。     

Changes in the northern Gulf of St. Lawrence ecosystem estimated by inverse modelling: Evidence of a fishery-induced regime shift?

Mass-balance models have been constructed using inverse methodology for the northern Gulf of St. Lawrence for the mid-1980s, the mid-1990s, and the early 2000s to describe ecosystem structure, trophic group interactions, and the effects of fishing and predation on the ecosystem for each time period. Our analyses indicate that the ecosystem structure shifted dramatically from one previously dominated by demersal (cod, redfish) and small-bodied forage (e.g., capelin, mackerel, herring, shrimp) species to one now dominated by small-bodied forage species. Overfishing removed a functional group in the late 1980s, large piscivorous fish (primarily cod and redfish), which has not recovered 14 years after the cessation of heavy fishing. This has left only marine mammals as top predators during the mid-1990s, and marine mammals and small Greenland halibut during the early 2000s. Predation by marine mammals on fish increased from the mid-1980s to the early 2000s while predation by large fish on fish decreased. Capelin and shrimp, the main prey in each period, showed an increase in biomass over the three periods. A switch in the main predators of capelin from cod to marine mammals occurred, while Greenland halibut progressively replaced cod as shrimp predators. Overfishing influenced community structure directly through preferential removal of larger-bodied fishes and indirectly through predation release because larger-bodied fishes exerted top-down control upon other community species or competed with other species for the same prey. Our modelling estimates showed that a change in predation structure or flows at the top of the trophic system led to changes in predation at all lower trophic levels in the northern Gulf of St. Lawrence. These changes represent a case of fishery-induced regime shift.     

Nematode community dynamics over an annual production cycle in the central North Sea

Nematode species composition, trophic structure and body size distributions were followed over an annual production cycle in the central North Sea; to test responses to temporally changing food quality and quantity in the sediment. Changes in the phytoplankton concentration in the water column were quantitatively reflected in the concentration of chlorophyll a and breakdown products in the sediment, with higher concentrations in spring and autumn following blooms, and lower concentrations in summer and winter. The taxonomic and trophic structure of nematode communities differed significantly among stations over relatively short distances, potentially masking some of the temporal dynamics. Spatio-temporal differences in nematode species composition were linked to changes in the quality and quantity of organic material reaching the seabed, reflecting a species-specific response to the nutritional quality of sedimenting organic material and the biochemical changes in the sediment associated with its decomposition. The size distributions of selected nematode species indicated that most species bred continuously throughout the sampling period, although one species, the epigrowth feeder Spilophorella paradoxa, had periods of increased growth following the deposition of the spring phytoplankton bloom. There was no consistent temporal relationship between the trophic composition of nematode communities and spring chlorophyll a or carbon sedimentation, most likely a result of the trophic plasticity of most feeding types and the capacity of the community to use both freshly sedimented material as well as the subsequent breakdown products and refractory organic matter. Community metrics implied that there were small responses to the seasonal production cycle, but these belied strong responses of a few species with life histories that allowed them to track the availability of suitable food resources.     

Comparing pristine and depleted ecosystems: The Sørfjord, Norway versus the Gulf of St. Lawrence, Canada. Effects of intense fisheries on marine ecosystems

The Sørfjord, Norway, and the Gulf of St. Lawrence, Canada, are two sub-arctic ecosystems with similar trophic structure. However, in the Gulf of St. Lawrence, severe exploitation of groundfish stocks has lead to important shifts in the trophic structure. In the Sørfjord, the situation is different: fishing pressure is much lighter. Our hypothesis is that overexploitation leads to changes in the trophic structure and severely alters the resilience of ecosystems. Based on the same modelling approach (Ecopath with Ecosim) the food web structure was compared, using different ecosystem indicators. Patterns of food web structure and trophodynamics were contrasted. Cod was the keystone species in both ecosystems, and forage fish were also important. Even after similar environmental changes in both ecosystems, and after a reduction of fishing pressure in the Gulf of St. Lawrence, there is no recovery of cod stocks in this ecosystem. In the Sørfjord, after different perturbations (but not from the fishery), the ecosystem seems to return to its equilibrium.     

Temporal Irregularities in the Macrobenthic Community and Deep-Water Advection in Wismar Bay (Western Baltic Sea)

Wismar Bay is a shallow coastal embayment in the Western Baltic Sea which is polluted by various industries. Macrobenthos data collected between 1986–91 are examined for qualitative and quantitative changes attributable to oxygen depletion and the subsequent time needed for recovery. Regular oceanographic surveys since 1976 indicate one episode of oxygen deficiency, caused by deep-water intrusion into the study area. However, principal component analyses show that the benthic community alternated between periods of relative stability and sudden change at both of the deeper sites examined. Deep-water intrusions from outside the bay are documented twice followed by sudden changes in the benthic community, but similar events may also have occurred in other years. The benthos showed little resilience when impacted, and the changes in the benthic community during July–August are proposed to monitor the future influence of the deep-water intrusions.