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1.
2.
William A. Gosline 《Ichthyological Research》1997,44(2-3):137-141
The basic function of the caudal skeleton in teleostean fishes is to support the caudal fin, but its parts contribute to this
function in somewhat different ways. The main axis for this support is the upturned terminal end of the vertebral column,
which ends at the base of the uppermost principal rays. The uroneural struts just ahead of this axis provide support for it.
The parts of the caudal skeleton behind and below this upturned axis, the hypurals and parhypural, not only support the caudal
rays but also provide a means for differential movements between the upper and lower parts of the fin base. This basic caudal
skeleton varies with the position of the fish in the sequence of teleosten evolution, the way in which the fish uses its caudal
fin, and to some extent with the shape of the fin. 相似文献
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5.
The opening of the Suez Canal in 1869 caused a migration generally from the Red Sea to the Mediterranean, rarely the opposite
direction, and 63 lessepsian fish species penetrated into the Mediterranean by way of this canal. These species usually spread
northward and most of them can establish wide populations in this area, but some of them can not be successful with respect
to establishment. Thus, it is clearly seen that there are a lot of factors influencing the success of species with respect
to migration, spreading and establishment. So, the lessepsian migration has been formed by the effects of these factors. Lessepsian
species also have the ability to adapt to the ecological conditions of their new environment. Therefore, the influential factors,
their effectiveness and the observed changes in lessepsian species due to the effects of these factors have been discussed
by considering fishes in this paper. 相似文献
6.
A brief review is provided in some advances in understanding the ecology of pike Esox
lucius Linnaeus over the last 10 years. Based on long-term studies and manipulative, often short-term experiments (laboratory, field
and mesocosms) several established theories have been supported, as well as new concepts developed. Despite their wide distribution
pike show low levels of polymorphism and divergence indicative of a recent common ancestral population. Recent genetic studies,
however, indicate a single refugium in North America compared to several refugia in Europe. Pike are found in rivers, lakes
and weakly saline waters. Variables such as growth and mortality are mainly affected by factors such as temperature, water
transparency, productivity, availability of prey and density of pike and other predators. In choice of habitat pike have been
shown to support the ideal free-distribution theory. The importance of macrophyte habitat in the life history of pike has
been reconfirmed and pike have been shown to be flexible in response to water clarity. Pike are extremely ‘plastic’ in choice
of prey types, prey size and in response to prey behaviour (e.g. they are unaffected by shoal size). Predation by pike not
only affects abundance and biomass of prey (including younger and smaller pike through cannibalism which plays a major role
in population dynamics, other fishes and invertebrates) but also evolution and adaptation of their morphology (in particular
body shape) and behaviours. There appears to be no relationship between stock and recruitment. Recruitment is influenced by
several abiotic factors in lakes and rivers. Pike play a major role in structuring freshwater communities and have been used
in stocking programmes to improve water quality (biomanipulation). Many new concepts have been developed in pike behaviour
in maximizing these stocking programmes both in biomanipulation and fisheries management. Despite many recent advances in
understanding the ecology of pike, particularly at the individual level, developments in quantifying and modelling the role
of pike as a top predator in large ecosystems have been limited, probably due to the difficulties of sampling natural populations.
Guest editors: J. M. Farrell, C. Skov, M. Mingelbier, T. Margenau & J. E. Cooper
International Pike Symposium: Merging Knowledge of Ecology, Biology, and Management for a Circumpolar Species 相似文献
7.
Jean‐Paul A. Hobbs Geoffrey P. Jones Philip L. Munday Sean R. Connolly Maya Srinivasan 《Journal of Biogeography》2012,39(1):130-139
Aim To determine the applicability of biogeographical and ecological theory to marine species at two remote island locations. This study examines how biogeography, isolation and species geographic range size influence patterns of species richness, endemism, species composition and the abundance of coral reef fishes. Location Christmas Island and the Cocos (Keeling) Islands in the tropical eastern Indian Ocean. Methods Published species lists and underwater visual surveys were used to determine species richness, endemism, species composition and abundance of reef fishes at the islands. These data were statistically compared with patterns of species composition and abundance from the neighbouring ‘mainland’ Indonesian region. Results The two isolated reef fish communities were species‐poor and contained a distinct taxonomic composition with an overrepresentation of species with high dispersal potential. Despite low species richness, we found no evidence of density compensation, with population densities on the islands similar to those of species‐rich mainland assemblages. The mix of Indian and Pacific Ocean species and the proportional representations of the various regional faunas in the assemblages were not influenced by the relative proximity of the islands to different biogeographical provinces. Moreover, species at the edge of their range did not have a lower abundance than species at the centre of their range, and endemic species had substantially higher abundances than widespread species. At both locations, endemism was low (less than 1.2% of the community); this may be because the locations are not sufficiently isolated or old enough to promote the evolution of endemic species. Main conclusions The patterns observed generally conform to terrestrial biogeographical theory, suggesting that similar processes may be influencing species richness and community composition in reef fish communities at these remote islands. However, species abundances differed from typical terrestrial patterns, and this may be because of the life history of reef fishes and the processes maintaining isolated populations. 相似文献
8.
Trophic diversity of the otter (Lutra lutra L.) in temperate and Mediterranean freshwater habitats 总被引:1,自引:0,他引:1
Aim To analyse the geographical patterns in the composition and diversity of otter's (Lutra lutra L.) diet and their relationship with climatic characteristics. Location European freshwater habitats under Mediterranean and temperate climatic regimes. Methods Thirty‐seven otter diet studies were reviewed, twenty‐one from temperate and sixteen from Mediterranean areas. All studies were based on spraint analysis and their results expressed as relative frequency of occurrence of seven main prey categories. Principal Component Analysis was performed to extract the main gradients of diet composition. Pearson's correlation and t‐tests were used to assess the relationship between diet characteristics (composition, diversity and taxonomic richness) and geographical and climatic variables. Results A clear latitudinal gradient in diet composition was observed. Otter diet was more diverse and featured more prey classes in southern localities, while the species was more piscivorous towards the north, where it predated upon a higher number of fish families. This pattern was similar when temperate and Mediterranean localities of Europe were compared. Mediterranean otters behaved as more generalist predators than temperate ones, relying less on fish, and more on aquatic invertebrates and reptiles. Main conclusions Geographical differences in otter feeding ecology in Europe seem to be related with the two contrasted climatic conditions affecting prey populations. The otter can act as a highly specialized piscivorous predator in temperate freshwater ecosystems, which do not suffer a dry season and have a comparatively stable water regime compared to Mediterranean ones. However, the unpredictable prey availability in Mediterranean areas, affected by strong spatial and temporal water shortages, favours a diversification of the otter's diet. 相似文献
9.
The fully enclosed Taiaro lagoon is hypersaline (42.5 psu) and non-tidal; constant salinity and water level result from strong
evaporation balanced by low percolation through the lagoon floor. Seawater can flow over the atoll rim during exceptionally
high seas and may then replenish lagoonal communities with propagules of oceanic origin. The distinctive water chemistry of
the lagoon suggests a possible way of identifying these immigrants. We established this potential by analysing stable isotopes
of carbon and oxygen in the recent growth layers of otoliths of two adult reef fishes, Chaetodon ulietensis and Acanthurus triostegus, collected from both sides of the atoll rim. Fish from the two locations were discriminated by their isotopic signatures,
suggesting that analysis of the microchemical signatures deposited during the larval development could be used in future work
to determine which individuals and species complete their life-cycles in this unusual lagoon.
Accepted: 28 August 1997 相似文献
10.
There is little understanding of how climate change will impact potamodromous freshwater fishes. Since the mid 1970s, a decline in annual rainfall in south‐western Australia (a globally recognized biodiversity hotspot) has resulted in the rivers of the region undergoing severe reductions in surface flows (ca. 50%). There is universal agreement amongst Global Climate Models that rainfall will continue to decline in this region. Limited data are available on the movement patterns of the endemic freshwater fishes of south‐western Australia or on the relationship between their life histories and hydrology. We used this region as a model to determine how dramatic hydrological change may impact potamodromous freshwater fishes. Migration patterns of fishes in the largest river in south‐western Australia were quantified over a 4 year period and were related to a number of key environmental variables including discharge, temperature, pH, conductivity and dissolved oxygen. Most of the endemic freshwater fishes were potamodromous, displaying lateral seasonal spawning migrations from the main channel into tributaries, and there were significant temporal differences in movement patterns between species. Using a model averaging approach, amount of discharge was clearly the best predictor of upstream and downstream movement for most species. Given past and projected reductions in surface flow and groundwater, the findings have major implications for future recruitment rates and population viabilities of potamodromous fishes. Freshwater ecosystems in drying climatic regions can only be managed effectively if such hydro‐ecological relationships are considered. Proactive management and addressing existing anthropogenic stressors on aquatic ecosystems associated with the development of surface and groundwater resources and land use is required to increase the resistance and resilience of potamodromous fishes to ongoing flow reductions. 相似文献