共查询到20条相似文献，搜索用时 461 毫秒
1.
2.
3.
4.
5.
《Journal of Sea Research》2007,57(2-3):230-235
The live body mass, body volume, and length were determined for four groups of juvenile plaice (Pleuronectes platessa L.): (1) plaice immigrating into the Wadden Sea, (2) fish that had settled in the Wadden Sea, (3) settled fish that had been starved, and (4) laboratory-reared fish. Mass and volume values were obtained by applying Archimedes' principle to weights of fish obtained while they were immersed in waters of different densities. The allometric relationship of mass, volume, and length was determined for each group using principal component analysis. Fish in each treatment group had different mass-volume-length trajectories. Immigrating fish had the least mass and volume at fixed length, followed by settled fish, and laboratory-reared fish had the greatest mass at fixed length. Mass and volume differences between freshly captured settled fish and starved fish were slight. All treatments showed great variability in body mass and volume at fixed length, and the use of fish length alone as an index of fish size is problematic. It is suggested that centroid size is a better measurement of fish size when size is an important variate in a study. 相似文献
6.
7.
Data on demersal fish abundance, distribution, and spatial variation in community composition are given for Vancouver harbour and a far field reference station in outer Howe Sound. Flatfish (F. Pleuronectidae) were the dominant taxa in the trawl sampling, with the English sole (Pleuronectes vetulus) one of the most abundant species, especially in Port Moody Arm. Cluster and ordination analyses suggested a different community in Port Moody Arm relative to the outer harbour and the reference site. Length data from English sole suggested the Vancouver harbour fish may be from a different population relative to the far field reference station, with more juveniles in the harbour. Both male and female English sole were older and larger in Port Moody Arm and females were more common in this area. Growth rates of female English sole were slower at Port Moody and Indian Arm in comparison to the central harbour. Feeding habits of English sole were different at various parts of the harbour, with possible implications for contaminant uptake. The diet of English sole was dominated by polychaetes in Port Moody Arm and by bivalve molluscs at the far field reference station. Fish from the middle and outer harbour fed on a mixture of polychaetes, bivalve molluscs, and crustaceans enabling multiple pathways for bioaccumulation of pollutants. 相似文献
8.
9.
10.
11.
《Journal of Sea Research》2007,57(2-3):187-197
To protect the main nursery area of plaice, an area called the ‘Plaice Box’ was closed to trawl fisheries with large vessels in 1989, with the expectation that recruitment, yield and spawning stock biomass would increase. However, since then the plaice population has declined and the rate of discarding outside the Plaice Box has increased, suggesting an offshore shift in spatial distribution of juvenile plaice. Using research vessel survey data collected since 1970, the change in distribution of juvenile age groups was analysed in relation to the distance to the coast. Further, a comparison of the distribution of different length classes of plaice between three historic periods was made (1902–1909; 1983–1987; 1999–2003). A shift towards deeper water of larger-sized plaice (20–39 cm) is apparent already before the 1980s and may be related to the decrease in the number of competitors or predators. An offshore shift in the distribution of young plaice occurred in the 1990s most likely in response to higher water temperatures that may have exceeded the maximum tolerance range or increased the food requirements above the available food resources. A decrease in competition with larger plaice offshore, possibly in combination with increased inshore predation by cormorants and seals, may also have played a role. The offshore shift in distribution has reduced the effectiveness of the Plaice Box as a technical measure to protect the under-sized plaice from discarding, since an increased proportion of the population of undersized plaice is moving to the more heavily exploited offshore areas. 相似文献
12.
13.
Distribution and quality of plaice (Pleuronectes platessa) nursery grounds on the Swedish west coast
《Journal of Sea Research》2007,57(2-3):218-229
Plaice (Pleuronectes platessa) has spatially restricted nursery grounds located in shallow soft bottom areas, where the nursery areas only make up a small fraction of the species distribution range. The importance of different coastal areas for recruitment is expected to depend on the quality and size of the nursery grounds. This paper describes the geographical extension of plaice nursery grounds at a regional level along the Swedish west coast. Densities of juvenile plaice were used as the response variable of habitat quality and were compiled based on records from autumn sampling in the various regions. Different aspects of nursery ground quality were related to the density of 0-group plaice, to evaluate the contribution of different factors to the geographical pattern observed. Larval supply was found to be the most important component of nursery quality showing a close relationship with the density of juvenile plaice on a regional scale. The relative contribution of plaice recruits from Swedish nursery grounds to the Skagerrak/Kattegat stock was evaluated using historical data. Swedish nursery grounds were estimated to contribute 77% of the recruits to the adult stock in the area. 相似文献
14.
15.
16.
17.
18.
19.
《Marine environmental research》1999,47(1):71-87
As in mammals, macrophages play a vital role in the destruction of infective organisms in fish. The current study was done to determine if exposure to polycyclic aromatic compounds (PACs), a group of chemical contaminants commonly found in the sediments of urban marine areas, alters the ability of peritoneal macrophages (MØs) from English sole (Pleuronectes vetulus) to produce cytotoxic reactive oxygen intermediates (ROIs). Initially, assay conditions including concentration of MØs, type of in vitro stimulant, tissue culture media, and incubation time were optimized to measure production of superoxide anion (O2−), the progenitor ROI, in English sole MØs. English sole were then injected with an organic solvent extract of a PAC-contaminated sediment equivalent to 20 g sediment (about 860 μg selected PACs) per kg fish, via their dorsal lymphatic sinus. Peritoneal MØs were harvested on days 1, 3, 7, and 14 post-injection. Elicited peritoneal MØs from English sole injected with the sediment extract produced significantly more O2− after stimulation in vitro with either opsonized zymosan on days 3 and 7 after exposure, or phorbol myristate acetate on day 7 when compared to the vehicle-injected or uninjected fish. Macrophages of fish injected with the vehicle responded comparably to those from uninjected individuals. No differences in the basal amounts of O2− production from activated peritoneal MØs were observed among the treatment groups. This study demonstrates that exposure of English sole to PACs altered macrophage production of O2−. Although the direct effects of the enhanced production of this ROI are unknown, the higher levels of superoxide anion production within peritoneal macrophages may contribute to immunodysfunction and oxidative damage in P. vetulus. 相似文献