摘要:

Feeding habits of larval pike,Esox luciusL., was studied at three stocking densities in illuminated cages. Developmental patterns of larval feeding on Zooplankton were independent of larval density. During the first week of rearing, larvae fed mainly on rotifers, small cladocerans, nauplii and copepodites of Cyclopidae. After second week they selected small cladocerans(Bosminaspp.), and adult copepods (CyclopsandMesocyclopsspp.). Higher stocking densities resulted in lower survival and growth rates. This was presumably due to increased competition for food, as the composition of the diet was independent of stocking density.

ISSN:1125-0003    

DOI:10.1080/11250009809386827

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The aim of this study was to estimate the composition of the diet and size‐related changes in the prey selection of pikeperch and pike in L. Peipsi. A total of 591 pikeperches with a standard length (Sl) of 9–73 cm and 254 pikes (Sl = 25–105 cm) were sampled with a bottom seine and an experimental trawl in 1994–1996 and their stomach content analysed. The frequency of occurrence and number of prey fish per individual were used for the description of the diet. The recent diet of pikeperch and pike in the Lake Peipsi were not exactly the same, although smelt, ruffe and perch were the main prey fishes of both. Smelt was the commonest in the diet of pikeperch in contrast to ruffe that was mainly taken by pike.

ISSN:1125-0003    

DOI:10.1080/11250009809386828

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The development of cannibalism of northern pike(Esox lucius)larvae was studied under controlled conditions. Pike larvae were reared in six glass, 50–1 aquaria at three stocking densities: 440, 2 200 and 4 400 larvae per aquarium. Fish were fedad libitumwithArtemianauplii and sieved Zooplankton. After 4, 8 or 12 days of rearing, pike larvae were anaesthetised and measured for total length (TL) and body weight (BW). Lowest survival and fish size were noted at the highest stocking density. The frequency of all cannibalistic attacks decreased in the order: highest > middle > lowest density; the frequency of successful attacks (expressed as the number of injured sibling fish) decreased, however, in opposite order.

ISSN:1125-0003    

DOI:10.1080/11250009809386829

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Artificial reef fish assemblages have the potential to alter the trophic structure of the nearby fauna by changing the available forage food. As the number and biomass of fish attracted to artificial reefs increases, they can reduce the potential energy available to sustain the assemblage. During 1994 we investigated the impact that artificial reef assemblages had on the proximate infauna in the forage area immediately surrounding several artificial reefs in the northern Gulf of Mexico. The forage community parameters (number of individuals, taxonomic richness, biomass, and diversity) were compared from areas which had no reefs to areas around reefs. Our analysis indicates there was considerable variation in the infauna in all areas. The number of individuals was lower near the reefs but was at the background level about 80 m from the reefs. Number of taxa was lower next to the reef and increased slightly away from the reefs but was much lower than background species richness. Species diversity was higher in the area near the reefs. To optimize the potential yield from artificial reefs, managers should recognize the potential impact that the reef fish assemblage can have on the available food resources needed to sustain a viable artificial reef fish assemblage.

ISSN:1125-0003    

DOI:10.1080/11250009809386830

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A three‐year investigation was conducted in littoral areas of Elba Island using visual census to investigate settlement and recruitment of several coastal fish species both unfished and those important to small‐scale fisheries. Fish microhabitat preferences at different stages of development were examined to determine features that make these coastal areas suitable for their settlement and recruitment. Post‐larvae and recruits of46species, belonging to 18 families, were observed in the study area; the most important families were labrids (11 species) and sparids (10 species). Many of the species observed settled in shallow water (< 1 m) and near shore (< 2 m from shore) of littoral rocky areas. Three sparids,Diplodus puntazzo, D. sargusandD. vulgaris, settle in shallow water with a slope of less than 30° and reduced algal cover. They have very similar spatial requests during the first year of their life and they use the nurseries at different time. This is probably an adaptive strategy to reduce inter‐specific competition among sea‐bream settlers and recruits. Knowledge of fish settlement and spatial requirements are important to develop models for integrated and sustainable coastal zone management.

ISSN:1125-0003    

DOI:10.1080/11250009809386831

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Fish community structure of the Island Lampedusa, with a special focus on the fish assemblage inhabiting the infralittoral rocky substrate, was studied from July to October 1995. Visual census techniques (strip transects and random censuses) and the application of an anaesthetic (quinaldine), to sample cryptic and benthic species, were used. A total of 77 species and 29 fish families were censused. The most common families were Labridae and Spari‐dae. Factor analysis applied to the 84 visual assessments, using the 9 most common species, divided the samples according to their position along the coast, depth, substrate, algae cover and presence of the vascular plant,Posidonia oceanica.In addition, discriminant analyses indicated the ecological preferences of some species. Size frequency distributions indicated the distribution of different life stages. Despite the shallow depths sampled, the present study shows how the fish community of this island has high species richness

ISSN:1125-0003    

DOI:10.1080/11250009809386832

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The coastal fish assemblage in the marine park of the Ustica Island was studied using underwater visual census. Seasonal surveys were conducted from May 1996 to March 1997 at several sites located within three zones of the reserve, each characterized by different levels of protection (integral reserve, general reserve and partial reserve). Visual strip transects were conducted using SCUBA at three different depth (3–5 m; 10–15 m; 25–30 m). Species richness and diversity indices were better correlated to depth than to protection level. Oppositely, size and/or abundance of some vulnerable species (e.g.,Epinephelus marginatus, Labnis me‐rula, Labrus viridis)were positively correlated with degree of protection and the so‐called ‘reserve effect’. These observations stress the importance of protection measures for littoral fish assemblages and represent the only available data for an Italian marine park of considerable extent.

ISSN:1125-0003    

DOI:10.1080/11250009809386833

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Data collected during four trawl surveys conducted in the Ionian Sea were used to describe the structure and spatial distribution of the demersal assemblages (fishes, crustaceans and cephalopods) on the bathyal grounds. Samples were taken from depths of 200 to 700 m during spring and autumn of 1994 and 1995. Classification and ordination of the demersal communities were conducted with cluster and correspondence analyses, respectively.

ISSN:1125-0003    

DOI:10.1080/11250009809386834

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Trawl samples were collected during two periods, autumn 1995 and winter 1996. A total of 2574 specimens per trawling hour (Nh‐1) composed of 105 species were collected in the Cyclades, while in the Saronikos the 1633 specimens (Nlr‐1) that were captured composed of 40 species. Species richness and the Shannon‐Wiener diversity index were higher values in the Cyclades. Higher diversity was recorded in the winter and in the 150–300 m depth zone in both locations. Similarity of the demersal fish communities in the two study areas were investigated using multivariate analysis. It appeared that the affinity of sampling sites, based on the composition of fish catches, was strongly influenced by depth.Trachurusspp (T.picturatusin shallow waters in autumn, andT. trachurusin deeper locations in autumn and in all depths in winter) dominated the Saronikos catches and contributed mainly to the dissimilarity that was displayed between the composition of the demersal fish communities.

ISSN:1125-0003    

DOI:10.1080/11250009809386835

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Turkish Island of Gökçeada is located in the northeastern Aegean Sea. In this preliminary study, six collecting stations, at depths 5–15 were sampled. A total of 76 species were collected by trammel and gill nets (59 species) or by trawls (17 species). At each station and during each season the Shannon‐Weaver Diversity index and Simpson Dominance index were calculated. These indices were compared with their mean values for each station. The similarity among the stations was estimated Sorenson's (1948) formula. Similarity index, stations I and III showed the highest similarity (80%), and stations IV‐VI (44%) and V‐VI (45%) showed the lowest similarity.

ISSN:1125-0003    

DOI:10.1080/11250009809386836

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor