Temporal consistency of ontogenetic shifts in habitat use by coral reef fishes in the northernmost coral ecosystem in the world (Kudaka Island, Japan)

The prevalence of major habitat shifts in tropical fishes between juvenile and adult stages (ontogenetic shifts) in one of the northernmost coral reefs in the world (Kudaka Island, Japan) is given. The comparative analysis of spatial distribution of juveniles v . adults highlighted four ontogenetic patterns: no change in habitat use between juveniles and adults (five species), a decrease in the number of habitats used by adults compared to juveniles (three species), an increase in the number of habitats used during the adult stage (four species) and use of nursery areas by juveniles followed by extensive movements to different adult habitats (three species). The comparative analysis of fish distribution over time ( i.e. during three consecutive settlement months) showed that 84% of species had temporal consistency in ontogenetic patterns of habitat use.     

Is artificial habitat diversity a key to restoring nurseries for juvenile coastal fish? Ex situ experiments on habitat selection and survival of juvenile seabreams

Man‐made infrastructures have become ubiquitous components of coastal landscapes, leading to habitat modification that affects the abundance and diversity of marine organisms. Marine coastal fish have a complex life cycle requiring different essential habitats. One of these habitats is known as a nursery, a place where juveniles can settle in large numbers, survive, and grow to contribute to the adult population. Nurseries are mainly found in shallow, sheltered zones and are thus particularly impacted by urbanization, notably by harbors. The vertical featureless structure of docks is very unlikely to be used by juveniles, which need complex habitats to find food and shelter from predators. Recent attempts to rehabilitate the nursery function in such environments by using artificial habitats have proven efficient in increasing juvenile densities. However, nothing is known about the survival of juveniles in these habitats, preventing any conclusions on the effectiveness of this means of restoration from being drawn. Here, we set up tank experiments to test the relationship between habitat preferences and the survival rate of two species of seabream when facing stalk‐attacking combers. Habitat choice was consistent with survival results, indicating that artificial habitats might not represent unintended ecological traps for juveniles. However, the artificial habitats' effect on survival was variable between species. Therefore, our results suggest that habitat diversity might be of prime importance to sustain juveniles of different species and stress the need for the development of diverse artificial habitats to counteract the effects of seascape homogenization.     

Development of dietary specializations in a summer community of juvenile fishes

Synopsis Patterns of food use and food availability were analysed in a species rich summer weedbed community of juvenile lake fish to elucidate ontogenetic and ecological adaptations facilitating species co-existence and rapid growth. It was found that: (a) the community was based on the period of high seasonal invertebrate abundance linked to the spring-summer proliferation of macrophytes: food was not limiting; (b) diet separations of individual fish species were high. In mid-July when nine species were present, Schoener diet overlap values exceeded 0.25 in only ten of 36 pairs of combinations. This contrasted with findings from a preceding May-June community of larval fish (Keast 1980); (c) mouth size helped channel the species towards different diets; and (d) diets of the early juveniles were distinct from those of the larvae, and late juveniles and adults of their species. At both the species and community level, ontogenetic and ecological developments have evolved in response to the opportunities created by an annually repetitive resource base.     

Seasonal trends and fish-habitat associations around Pari Island, Indonesia: setting a baseline for environmental monitoring

Indonesia is the world??s richest country regarding reef fish diversity. Nevertheless, the reef ichthyofauna of the Indonesian Archipelago remains poorly known, primarily due to a lack of sampling. Coral reefs in the Kepulauan Seribu Marine National Park close to the Indonesian capital Jakarta are under threat by many destructive activities that trigger a loss of habitat and species diversity. This communication: (1) describes the reef fish community structure from three distinct reef habitats in the Pari Island group dominated by Acropora branching corals (ACB), foliose corals (CF) and massive corals (CM), using a number of community properties such as numerical abundance, species richness, diversity, and multivariate similarity; (2) examines the temporal variation of the fish community from the three habitats; and (3) discusses possible implications for the monitoring of qualitative changes in coral reef systems on small islands. During this study, a total of 13 536 individual fishes were counted, representing 205 species belonging to 36 families. In terms of species richness, Pomacentridae was the dominant fish family in ACB and CF sites (40?% and 48.6?%, respectively), and Labridae (27.4?%) was the dominant family in the CM plots. The most species-rich habitat was ACB with 125 species (with Amblyglyphidodon curacao as the most characteristic species), followed by CM and CF with 117 (Thalassoma lunare) and 79 species (Pomacentrus alexanderae), respectively. Average Shannon-Wiener diversity (ln basis) ranged from 2.0?C2.9 (ACB), 2.4?C3.1 (CF), and 2.1?C3.0 (CM), with no significant difference between growth forms. Abundance, species richness and diversity showed significant seasonal variability, but the effects differed between habitats. Multivariate analysis of the reef fish community was able to detect significant differences between species composition and diversity of the reef fish community between sites with different coral growth forms at Pari Island, both when based on species abundances and when aggregated according to trophic categories. It thus constitutes a useful tool to detect qualitative differences of the species-rich Indonesian coral reef ecosystems.     

Biogeographical affinities,trophodynamics, and fisheries pressure in the fish community of the Laguna Madre Tamaulipas

The Laguna Madre Tamaulipas (LMT) is the largest hyperhaline coastal lagoon of Mexico, is diverse and provides a wide range of services, besides its economic importance for local and national fisheries. However, due to global and local pressures, the fish community is under stress. Here we study the LMT fish community to determine its biogeographical affinities with the Gulf of Mexico and Caribbean, understand its trophic relationships and habitat distribution, and to analyze the fisheries pressures in specific habitats and trophic groups (TGs). Our biogeographical analyses based on Parsimony Analysis of Endemism produce three provinces Center, South, and Northern, being this last the most related to the LMT, thus activities in this and the LMT directly affect each other. Through a nested cluster analysis using trophic values and size, 15 TGs were found, being the small‐species the most diverse and the largest the less diverse and most targeted by fishermen, which put on risk its ecological role and may provoke cascading effects on many species and processes. As well, mangroves and oyster banks habitats are supporting most of the fisheries. This is the first study of the whole fish community of the LMT, we pinpoint provinces, habitats, and TGs that need special attention and constant monitoring to generate integrative management plans that fit the actual needs of the community and prepare it to buffer future changes.     

东海大陆架鱼类群落的空间结构

根据1997～2000年东海大陆架水深30～200米海域4个航次的底拖网调查资料,运用多元分析(聚类分析和非度量多维标度(NMDS))、SIMPER以及BIO-ENV方法分析了东海鱼类群落的空间格局以及与非生物环境因子之间的关系。结果表明,东海大陆架海域鱼类群落在空间上可分为3个群落类型,分别为东海近海群落、东海大陆架外缘群落以及这两个群落之间的东海大陆架混合群落。东海大陆架鱼类群落的种类组成沿着水深梯度的变化明显,每种鱼类均有一定的水深范围。不同的流系具有不同的温盐特征,影响了鱼类的分布及其洄游,从而控制了不同鱼类群落类型的种类组成。东海大陆架鱼类群落类型中,大陆架外缘群落类型各调查季节在空间分布和种类组成上相对稳定,而东海近海群落类型和东海大陆架混合群落类型在夏季融合在一起,其它季节保持各自的空间结构。同时东海陆架区只在一种群落类型中出现的鱼类相对较少,多数鱼类同时出现在两个群落类型中或3个群落类型中,但是它们相对较集中的区域明显不同,在不同群落类型中的生物量和出现频率有很大的差异,这些鱼类在其不同的生长发育阶段由于对海洋环境的不同需求,它们根据繁殖或摄食需求而在东海陆架区范围内洄游以寻找最适的海洋环境,因此对3个群落类型定义是相对的,很难严格确定一个永久的鱼类群落地理区域,以形成相互隔离的鱼类群落,而且鱼类群落之间的边界随着季节不同发生变化。     

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.     

Spatial and temporal variation in fish community structure of a marine embayment in Zanzibar,Tanzania

Spatial and temporal variation in the fish community structure were studied in a tropical non-estuarine embayment in Chwaka Bay, Zanzibar (Tanzania). Fish samples were collected bi-monthly (at each spring low tide) for 1 year (November 2001–October 2002) from a range of bay habitats ranging from mangroves deep inside the bay to seagrass beds close to the mouth of the bay. Additionally, environmental variables were examined to determine their relationship with the fish community structure. Being a non-estuarine embayment, the environmental variables as well as the fish community structure in each habitat remained relatively constant for most part of the year; however, a marked decline was observed during the rainy period (April–May). Significant variations in fish community variables (density, biomass and species richness) and in water temperature and salinity were observed during the rainy season in all habitats, with larger changes in the mangrove and mud/sand flats habitats than in the seagrass beds. Seasonal variations in water clarity and dissolved oxygen were not significant, though. Many species disappeared from the mangrove and mud/sand flats habitats during the rainy season and those which persisted showed a remarkable decrease in density. Moreover, the results indicate that mangroves were the preferred settling habitats for Gerres filamentosus, Gerres oyena, Lethrinus lentjan and Monodactylus argenteus, especially during the dry period (December–February) before the rainy season. This observation is contrary to what has been reported from some other tropical regions where greater abundance and species richness was observed during the rainy season. A significant relationship was found between density of fish and temperature, salinity and turbidity. Since salinity was the most conspicuously changing environmental variable with seasons, we propose that salinity, alone or in combination with low visibility and temperature, was probably the most important environmental factor structuring the fish assemblage in the mangrove and mud/sand flats habitats, particularly during the rainy season. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: J. A. Cambray     

The fish community of a high mountain stream in Taiwan and its relation to dam design

Synopsis The fish community of a high mountain stream in Taiwan was studied from 1988 to 1990 in a 16 km section of Ta-chia river where a new dam is planned for construction. There were 16 species of fish belonging to 7 families; 15 genera were recorded. Six species are endemic to Taiwan. The dominant species wereZacco pachycephalus, Acrosscheileus paradoxus andRhinogobius brunneus. The composition of fish fauna was different between the eight study sites. Adjacent sites did not show a higher similarity than remote ones. AdultZ. pachycephalus andA. paradoxus showed seasonal aggregation behavior in the stream. At two distinct sites, Kukan and Tungmau, these two species had similar breeding and stock composition patterns with an intensified production period of juveniles from late autumn to early winter and a low, but continuous production period of juveniles in summer months. This information suggest that fishes in the river have special adaptations to the typhoon season in summer and benthic algal blooming in winter. The similarity of fish community and the independent breeding sites of endemic fishes in Kukan and Tungmau also suggest that these are important factors to consider for conservation when the flooding area of a high mountain dam is designed.     

Recruitment patterns and trophic relationships of fish in Sulaibikhat Bay, Kuwait

The juveniles of nine species of fish constitute over 96% of the fish community captured in Sulaibikhat Bay, a shallow, semi-enclosed bay located at the northern end of the Persian Gulf. These juveniles show four patterns of recruitment to the bay, including recruitment in early spring, in late spring, in summer and all year round. Stomach content analysis allowed five groups of diets to be distinguished. Within these five groups, competition for food resources was probable, particularly in the spring and autumn months.     

Two endemic and endangered fishes, Poecilia sulphuraria (Alvarez, 1948) and Gambusia eurystoma Miller, 1975 (Poeciliidae, Teleostei) as only survivors in a small sulphidic habitat

In the Baños del Azufre in Tabasco, Mexico, only two poeciliid species, Poecilia sulphuraria and Gambusia eurystoma , were found in sulphidic habitats, whereas adjacent non-sulphidic habitats were characterized by a vastly different fish community. Exposure of fishes to water from a sulphidic spring showed that all species except for P. sulphuraria quickly lost motion control, probably because of the toxic properties of H₂S. It is suggested that the fishes endemic to the Baños del Azufre are highly specialized, and competitive exclusion allows them to survive only in this particular habitat type.     

The Mangrove Nursery Paradigm Revisited: Otolith Stable Isotopes Support Nursery-to-Reef Movements by Indo-Pacific Fishes

Mangroves and seagrass beds have long been perceived as important nurseries for many fish species. While there is growing evidence from the Western Atlantic that mangrove habitats are intricately connected to coral reefs through ontogenetic fish migrations, there is an ongoing debate of the value of these coastal ecosystems in the Indo-Pacific. The present study used natural tags, viz. otolith stable carbon and oxygen isotopes, to investigate for the first time the degree to which multiple tropical juvenile habitats subsidize coral reef fish populations in the Indo Pacific (Tanzania). Otoliths of three reef fish species (Lethrinus harak, L. lentjan and Lutjanus fulviflamma) were collected in mangrove, seagrass and coral reef habitats and analyzed for stable isotope ratios in the juvenile and adult otolith zones. δ¹³C signatures were significantly depleted in the juvenile compared to the adult zones, indicative of different habitat use through ontogeny. Maximum likelihood analysis identified that 82% of adult reef L. harak had resided in either mangrove (29%) or seagrass (53%) or reef (18%) habitats as juveniles. Of adult L. fulviflamma caught from offshore reefs, 99% had passed through mangroves habitats as juveniles. In contrast, L. lentjan adults originated predominantly from coral reefs (65–72%) as opposed to inshore vegetated habitats (28–35%). This study presents conclusive evidence for a nursery role of Indo-Pacific mangrove habitats for reef fish populations. It shows that intertidal habitats that are only temporarily available can form an important juvenile habitat for some species, and that reef fish populations are often replenished by multiple coastal habitats. Maintaining connectivity between inshore vegetated habitats and coral reefs, and conserving habitat mosaics rather than single nursery habitats, is a major priority for the sustainability of various Indo Pacific fish populations.     

Variation in Vertebral Number in Galaxiid Fishes (Teleostei: Galaxiidae): A Legacy of Life History, Latitude and Length

Mean vertebral counts among species of Galaxiidae vary curvilinearly with fish size – large species have more vertebrae (pleomerism). The relationship with size breaks down among adults of diadromous species. There is mostly no relationship between vertebral count and body shape, although an inverse relationship between count and body depth in a series of divergent small galaxiids may reflect a shift in swimming mode. Diadromous populations have more vertebrae than non-diadromous (landlocked) conspecifics (around the same number as related non-diadromous species). Diadromous species have more vertebrae than related non-diadromous species and exhibit rising vertebral number with increasing latitude (Jordan's rule applies). Regressions of vertebral number against latitude differ among conspecific populations from different regions, perhaps reflecting different relationships between latitude and local climate. Differences in counts between diadromous and non-diadromous species are not simply a direct influence of environment on ontogeny, as embryonic development of species/populations undertaking the two distinct life history strategies occurs in similar, freshwater habitats; differences seem likely to be evolved, and to reflect an advantage of higher vertebral counts in marine environments, where diadromous species live as juveniles. This conclusion is supported by correlation between vertebral counts and size of juveniles of diadromous species at return from the sea, suggesting selection for vertebral number during marine life. Overall, vertebral count is thus influenced by a complex amalgam of fish size, life history, and environment. The explanation for pleomerism may well be related to the scaling relationship between length and cross-sectional area (area rises by the square of length increase) leading to increasing stiffness with growth – compensated for in larger species by having more vertebrae. This could also be driven by scaling in the surface area of the articular facets of the vertebrae themselves.     

The importance of mangroves, mud and sand flats, and seagrass beds as feeding areas for juvenile fishes in Chwaka Bay, Zanzibar: gut content and stable isotope analyses

The relative importance of bay habitats, consisting of mangrove creeks and channel, seagrass beds, and mud and sand flats, as feeding grounds for a number of fish species was studied in Chwaka Bay, Zanzibar, Tanzania, using gut content analysis and stable isotope analysis of carbon and nitrogen. Gut content analysis revealed that within fish species almost the same food items were consumed regardless of the different habitats in which they were caught. Crustaceans (mainly copepods, crabs and shrimps) were the preferred food for most zoobenthivores and omnivores, while fishes and algae were the preferred food for piscivores and herbivores, respectively. The mean δ¹³C values of fishes and food items from the mangrove habitats were significantly depleted to those from the seagrass habitats by 6·9 and 9·7‰ for fishes and food items, respectively, and to those from the mud and sand flats by 3·5 and 5·8‰, respectively. Fishes and food items from the mud and sand flats were significantly depleted as compared to those of the seagrass habitats by 3·4 and 3·9‰, for fishes and food, respectively. Similar to other studies done in different geographical locations, the importance of mangrove and seagrass themselves as a primary source of carbon to higher trophic levels is limited. The different bay habitats were all used as feeding grounds by different fish species. Individuals of the species Gerres filamentosus , Gerres oyena , Lethrinus lentjan , Lutjanus fulviflamma , Pelates quadrilineatus and Siganus sutor appeared to show a connectivity with respect to feeding between different habitats by having δ¹³C values which were in-between those of food items from two neighbouring habitats. This connectivity could be a result of either daily tidal migrations or recent ontogenetic migration.     

Habitat preference in newly settled coral trout (Plectropomus leopardus, Serranidae)

 The densities of newly settled coral trout (Plectropomus leopardus, Pisces, Serranidae) were monitored in a variety of habitats on Green Reef in the Cairns section of the Great Barrier Reef to assess whether spatial patterns of recruitment are influenced by physical features of the substratum, and whether this species uses different habitats during its ontogeny. Surveys showed that small juveniles used sites that were significantly different from random and that these habitat associations changed as the fish grew larger. Specifically, coral trout recruited to level patches of rubble substrata >5 m² and subsequently shifted to high relief features. Densities of recruits were related to the amount of rubble substrata available. Accepted: 4 July 1996     

Fish Assemblages Associated with Natural and Anthropogenically-Modified Habitats in a Marine Embayment: Comparison of Baited Videos and Opera-House Traps

Marine embayments and estuaries play an important role in the ecology and life history of many fish species. Cockburn Sound is one of a relative paucity of marine embayments on the west coast of Australia. Its sheltered waters and close proximity to a capital city have resulted in anthropogenic intrusion and extensive seascape modification. This study aimed to compare the sampling efficiencies of baited videos and fish traps in determining the relative abundance and diversity of temperate demersal fish species associated with naturally occurring (seagrass, limestone outcrops and soft sediment) and modified (rockwall and dredge channel) habitats in Cockburn Sound. Baited videos sampled a greater range of species in higher total and mean abundances than fish traps. This larger amount of data collected by baited videos allowed for greater discrimination of fish assemblages between habitats. The markedly higher diversity and abundances of fish associated with seagrass and limestone outcrops, and the fact that these habitats are very limited within Cockburn Sound, suggests they play an important role in the fish ecology of this embayment. Fish assemblages associated with modified habitats comprised a subset of species in lower abundances when compared to natural habitats with similar physical characteristics. This suggests modified habitats may not have provided the necessary resource requirements (e.g. shelter and/or diet) for some species, resulting in alterations to the natural trophic structure and interspecific interactions. Baited videos provided a more efficient and non-extractive method for comparing fish assemblages and habitat associations of smaller bodied species and juveniles in a turbid environment.     

210Pb dating by low background gamma counting

An intertidal fish community in Trinidad Bay, Humboldt County, California, was studied between November 1968 and May 1970. The nursery function of rocky tidal pools for juveniles of subtidal fishes was indicated by peaks in indices of seasonally abundant fish species in summer. The proportion of juveniles of seasonal species in the intertidal fish community rose significantly in collections of late spring and summer, to a maximum of 35% of the individuals collected in July. Annual dominance was relatively high due to abundant populations of the tidepool sculpin, Oligocottus maculosus, but two other fish species were also encountered in tidepools every month of the year.     

Biology of the cardinalfishGlossamia gjellerupi (Perciformes: Apogonidae) from the Sepik-Ramu River basin,Papua New Guinea

Synopsis Glossamia gjellerupi forms a considerable part of the fish biomass (25%) and density (12%) in floodplain margin streams and lower foothill streams throughout the Sepik-Ramu basin where it occurs up to an altitude of 320 meters above sea level. It prefers habitats with slow flow rates: pools, alongside banks, under cover of vegetation, etc. Biomass and density decreased with increasing current speeds. Condition factor and fat deposits were negatively correlated to current speeds, with populations from floodplain margin streams having the highest averages for both these indices. Fluctuations in population size appeared to be related to the irregular occurrence of spates. No seasonality in reproduction, condition and fat deposits were noted although peaks occurred according to specific local conditions. Fecundity was found to be low, increasing with fish size. Eggs in a ripe ovary were all in the same stage of development, with sizes of around 3.3 mm.G. gjellerupi is a male mouth brooder. Mouth-breeding may restrict the species to well oxygenated waters. Reproductive activity takes place throughout the year but is not random since clear peaks in gonad development occurred within different populations. Reproductive activity and/or survival rate of juveniles are possibly directly related to floods. Prolonged periods of environmental stability, such as those occurring in periods of less rainfall, seem to be conditional for the survival of juveniles. Fish up to 30 mm length fed predominantly on small benthic insect larvae. Fish larger than 60 mm are carnivorous top-predators feeding predominantly on crabs, bottom dwelling fish and large terrestrial insects. Fish of all sizes, except the largest, fed on caridinid prawns. Feeding habits varied between different habitats depending on local environmental conditions.     

Global ecological impacts of invasive species in aquatic ecosystems

The introduction of invasive species, which often differ functionally from the components of the recipient community, generates ecological impacts that propagate along the food web. This review aims to determine how consistent the impacts of aquatic invasions are across taxa and habitats. To that end, we present a global meta‐analysis from 151 publications (733 cases), covering a wide range of invaders (primary producers, filter collectors, omnivores and predators), resident aquatic community components (macrophytes, phytoplankton, zooplankton, benthic invertebrates and fish) and habitats (rivers, lakes and estuaries). Our synthesis suggests a strong negative influence of invasive species on the abundance of aquatic communities, particularly macrophytes, zooplankton and fish. In contrast, there was no general evidence for a decrease in species diversity in invaded habitats, suggesting a time lag between rapid abundance changes and local extinctions. Invaded habitats showed increased water turbidity, nitrogen and organic matter concentration, which are related to the capacity of invaders to transform habitats and increase eutrophication. The expansion of invasive macrophytes caused the largest decrease in fish abundance, the filtering activity of filter collectors depleted planktonic communities, omnivores (including both facultative and obligate herbivores) were responsible for the greatest decline in macrophyte abundance, and benthic invertebrates were most negatively affected by the introduction of new predators. These impacts were relatively consistent across habitats and experimental approaches. Based on our results, we propose a framework of positive and negative links between invasive species at four trophic positions and the five different components of recipient communities. This framework incorporates both direct biotic interactions (predation, competition, grazing) and indirect changes to the water physicochemical conditions mediated by invaders (habitat alteration). Considering the strong trophic links that characterize aquatic ecosystems, this framework is relevant to anticipate the far‐reaching consequences of biological invasions on the structure and functionality of aquatic ecosystems.