摘要:

The removal of tropical forest cover during timber extraction represents an extreme form of disturbance, with potentially far‐reaching effects on fish biodiversity. Fish populations were quantified in streams running through a mosaic of unlogged and selectively‐logged areas in Sabah, East Malaysia to assess these effects. A diverse assemblage of more than thirty species of fish were found in both sets of streams with little or no evidence of loss of biodiversity in streams in logged forest, although shifts in dominance were recorded from slow‐water communities. Additional data were provided by monitoring fish populations before selective logging operations and for eighteen months subsequently. Increases in diversity and species number were recorded from one site for 15 months from the start of sampling, but two other sites showed little change. Explanations for the persistence of the fish community in the face of high disturbance pressure include high rates of colonisation and movement from undisturbed areas and/or avoidance or tolerance of disturbance effects.

ISSN:1125-0003    

DOI:10.1080/11250009809386847

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The requirement for fish stock conservation became law in 1991 at the same time of the declaration of the Danube Delta as a Biosphere Reserve. Conservation of biodiversity is the major objective of the reserve, with sustainable use of fish stocks introduced as the target objective in the fisheries. The present threat is over‐fishing by more fishermen with new fishing gears entering the fishery after abandonment state monopoly economy. The introduction of a Total Allowable Catch was the first strategy adopted for the sustainable use of the fish resources. Poor quality of catch data, lack of fishing effort data, and unfulfilled model assumptions in the estimation of Maximum Sustainable Yield are the principal constraints to achieve this goal. Limiting the fishery to 1000 individual fishing licenses should be one practical regulation for fish stock conservation.

ISSN:1125-0003    

DOI:10.1080/11250009809386848

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Perca schrenkiis endemic to the Balkhash ichthyogeographic province in Kazakhstan and historically inhabited various ecological regions within the basin. Its distribution has been considerably reduced because of the introduction of many other species, although it still occurs in the Alakol lakes, where a fishery thrives, and in some outlying areas of the basin. The Balkhash‐Ili population ofP. schrenkiwas considered endangered several years ago, but, in fact, these populations are now extirpated. During the 1960s,P. schrenkiwas introduced outside of its native range. Populations now exist in the basins of the Rivers Nura, Olenty and Chu, as well as in some lakes in northern Kazakhstan. This expansion has resulted in hybridization betweenP. schrenkiandP. fluviatilis‐species that were previously reproductively isolated.

ISSN:1125-0003    

DOI:10.1080/11250009809386849

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Given the role of algae as primary producers and the possibility of reduction in their numbers by some fish species, as well as possible food competition between some autochthonous and allo‐chthonous fishes which are consumers of algae, feeding of two autochthonous species (carp and roach) and two allochthonous species (crucian carp and bighead carp) was investigated. Investigations were carried out in the following aquatic ecosystems: Sta‐ri Begej, Palicko Jezero and Bukinski Rit which are parts of the legally protected areas (nature reserves). All investigated aquatic ecosystems are eutrophic ones, characterized by high density of phytoplankton communities in which Bacillariohyta and Chlorophyta are the dominant algal groups. Feeding spectra preliminary investigation showed that algae take an important place in feeding of investigated fish species. Analyses of the algal component showed that participation of the different algal groups varied, but, generally, Bacillariophyta and Chlorophyta were dominant, which correspond to their domination in the waters. Detailed analyses of the algal component showed that, concerning the contribution of algal groups, there were no significant differences between the investigated fish species. It suggests likely possibility for food competition, as well as that some autochthonous species, such as the carp and roach, can decrease the density of algae as successful as the allochthonous ones, such as the crucian carp and bighead carp. Given that all of the investigated water bodies are the parts of protected areas characterized by a high diversity of autochthonous species, and that the allochthonous species can be a real threat to them, it is necessary to carry out measures directed to reducing the numbers or eliminating the allochthonous species from the protected water bodies.

ISSN:1125-0003    

DOI:10.1080/11250009809386850

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Umbra krameriis one of three representatives of the genusUmbrain Holarctic region, and the only native species in Europe. During the last few decades it has been reduced in range and abundance in all countries of known historical occurrence. The main reasons for its decline are habitat reduction and water pollution. Distribution records ofU. krameriin Serbia are scarce, but it is protected there as a natural rarity. The results of preliminary investigations on its distribution in Serbia show that this fish can still be found in suitable aquatic habitats, such as the stream Za‐savica.

ISSN:1125-0003    

DOI:10.1080/11250009809386851

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Miramare Reserve, in the Gulf of Trieste (North Adriatic‐Italy), is a small marine protected area (121 hectares) for research, education and conservation and is managed by WWF Italy. Different techniques for taking a qualitative and quantitative census of the fish species, for mapping the nests ofGobius cruentatus, Tripterygion delaisiandCbromis chromis, for studying the reproductive behaviour ofC. cbromisand for measuring the sea ambient noise were used. Visual census techniques were applied in the comparison of two areas which were similar from a morphological point of view, but differed in human activity.

ISSN:1125-0003    

DOI:10.1080/11250009809386852

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Site attachment, social organization and reproduction traits of the damselfish (Pomacentridae), based on field observations and cytology of gonads, are described. This fish family includes both solitary and gregarious species, as well as species of an intermediate nature. Many of the species are monodomous, using a specific, permanent habitat, whereas others are polydomous, occurring in different habitats or changing their habitat with age. Some of the species are monomorphic, developing their permanent colour when very young, whereas others are polymorphic, demonstrating different colour morphs as juveniles, particularly blue and yellow patterns. The damselfishes include gonochorists, with predetermination of sex, protogynous and protandrous hermaphrodites, and bisexual types in which the gonadal primordi‐um bears both types of gonia. With few exceptions, the polydomous species are primarily gonochorists, and the monodomous ones are hermaphrodites, in which sex determination is socially controlled depending on the type and composition of the surrounding group of conspecifics.

ISSN:1125-0003    

DOI:10.1080/11250009809386853

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Most flatfish have a white lower blind side and a brown or grey upper ocular side which can display cryptic patterning with dark areas and white spots. Active predatory flatfish likeReinbardtius hippoglossoideshave complete ambicoloration and this can also occur partly or completely in other flatfish such asPleuronectes americanus.Both hypermelanosis and hypomelanosis can occur in aquacultured flatfish. Dermal and epidermal melanophores, xanthophores and iridophores occur in various flatfish species and patterning has a morphological basis with differences in the size and frequency of chromatophores. The patterning is also physiological displaying differential responsiveness to background and stress. InPleuronectes americanuschromatic decentralization and hypophysectomy demonstrate that the pattern‐related responsiveness of melanophores is neurally controlled and that xanthophores are regulated by the pituitary.In vitropharmacology indicates that α‐adrenoceptors mediate melansome aggregation and β2‐adrenoceptors mediate dispersion. There is a pattern‐related differential balance in a and β‐adrenoceptor sensitivity but experiments after chemical sympathectomy suggest the additional participation of modulatory factors.

ISSN:1125-0003    

DOI:10.1080/11250009809386854

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Salt marsh environments are stressful, partially because of regular or unpredictable variations in ambient salinities, limiting habitability to a few teleost fish species. This study reviews capabilities of physiological response to ambient salinity in 10 teleost species of Florida Gulf coast salt marshes, nine permanent residents, and one a seasonal inhabitant. Two additional species found in marshes elsewhere in Florida, but absent from the study site, were also included. We examined salinity tolerances and osmotic regulatory capabilities among these teleosts, and related differences in their physiological responses to patterns of utilization of salinity‐habitat zones, fresh to hypersaline waters. Lower salinity tolerance varied from fresh water to dilute brackish water, while upper salinity tolerance varied from 25 ppt to >100 ppt within this group. Osmotic regulatory capabilities also varied within the group, with the ambient salinity zone of most consistent plasma osmotic regulation varying in width, and in position at lower or higher ambient salinities, and varying among species. This was also true of the levels at which plasma osmotic concentrations were maintained. Several patterns of physiological responses to ambient salinity were found, with these roughly correlated with ranges of ambient salinity inhabited by the various species.

ISSN:1125-0003    

DOI:10.1080/11250009809386855

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The regression between the yield of fish (Y) and the mean annual temperature of air (TEMP) both for geologically old lakes with endemic lacustrine fish fauna and those of the relatively recent origin inhabited by riverine species is the same. In contrast, the dependence of Y on the morphoedaphic index (MEI) in lakes with endemic lacustrine fish species differs strongly from that for lakes with riverine fish communities giving the predicted Y about three times higher for the former in comparison with that of the latter. The higher trophic efficiency of ancient lakes with endemic fish faunas is a consequence of the presence of pelagic species. Contrary to this, recent lakes are inhabited with riverine species dwelling along the shores leaving pelagic niche unoccupied.

ISSN:1125-0003    

DOI:10.1080/11250009809386856

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor