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1.
Abstract –  Stable isotopes of carbon and nitrogen ( δ 13C and δ 15N) were examined in wild and aquaculture origin Atlantic salmon, Salmo salar , to evaluate their utility to identify escaped farmed fish. Samples of muscle tissue obtained from wild Conne River, Newfoundland, salmon were significantly more enriched in nitrogen ( δ 15N: mean = 12.75; SD ± 0.38‰) but depleted in lipid corrected carbon ( δ 13C': mean = −20.51; SD ± 0.23‰) by comparison with aquaculture specimens obtained from Bay d'Espoir, Newfoundland ( δ 15N = 10.96 ± 0.19‰;  δ 13C' = −19.25 ± 0.17‰) resulting in a complete separation of the two groups. Aquaculture specimens differed in δ 13C' from analyses of commercial salmon diet by 0.24‰, within the enrichment range associated with trophic transfers, while the δ 15N values in salmon muscle were enriched by 5.01‰. Although differences occurred in direct comparisons of white muscle and adipose tissue ( N  = 49), the average δ 13C' and δ 15N signatures varied in absolute amounts by only 0.5‰, supporting the use of adipose tissue as a nonlethal means to determine isotopic signatures of Atlantic salmon.  相似文献   

2.
For developing efficient diets, two sets of experiments examined whether the use and allocation of dietary protein can be traced by labelling with stable isotopes (15N and 13C) in two culture fish ( Oncorhynchus mykiss and Sparus aurata) . In the first experiment, natural abundance and tissue distribution of these isotopes were determined, by measuring the δ13C and δ15N values by isotopic ratio mass spectrometry, in fingerlings (14–17 g) adapted to diets differing in the percentage of fish meal replacement by plant protein sources. For both species, δ15N and δ13C were greater in tissues with higher protein and lower lipid content. Delta 15N of diets and tissues decreased as replacement increased, suggesting δ15N can be used as a marker for dietary protein origin. The 15N fractionation (δ15N fish − δ15N diet) differed between groups, and could thus be used to indicate protein catabolism. In the second experiment, fish (75–90 g) of each species ingested a diet enriched with 15N-protein (10 g kg−1 diet) and 13C-protein (30 g kg−1 diet). These proportions were suitable for determining that the delta values of tissue components were high enough above natural levels to allow protein allocation to be traced at 11 and 24 h after feeding, and revealed clear metabolic differences between species.  相似文献   

3.
ABSTRACT:   It is important to clarify trophic dynamics in marine ecosystems for management of the fishing ground. Organic carbon sources and trophic position of pelagic fishes in the coastal waters of the south-eastern Izu Peninsula, Japan, were examined on the basis of carbon and nitrogen stable isotope distributions. The δ13C of the fishes was mostly distributed from −19 to −16‰ for nektonic fishes (13 species of adults and immatures) and planktonic fishes (10 species of larvae and juveniles), close to the δ13C values of particulate organic matter and planktonic decapods. These δ13C signatures for the inhabitants of the water column were in contrast with the high δ13C values (mainly −16 to −13‰) for demersal fishes of Scorpaeniformes and benthic polychaetes collected in the surf zone. These results indicate that nektonic and planktonic fishes depend on phytoplankton for carbon supply. The δ15N signatures suggest that the trophic position ranged 3.1–4.5 for the nektonic fishes and 2.9–3.7 for the planktonic fishes, premised on trophic level 3 for larval Japanese anchovy Engraulis japonicus . Thus, planktivorous fishes should be mainly assigned to trophic levels 3 and 4 in this area.  相似文献   

4.
ABSTRACT:   Stable carbon and nitrogen isotope ratios were determined in the baleen plates of 17 common minke whales Balaenoptera acutorostrata from the north-western Pacific Ocean off Japan, as well as prey species (krill Euphausia pacifica , Japanese anchovy Engraulis japonicus and Pacific saury Cololabis saira ) collected in the stomach contents, to investigate the trophic relationship between the minke whales and their prey. A few δ15N-depleted peaks occurred along the length of baleen plates for 10 males irrespective of stomach content (anchovies and sauries). Similar δ15N-depleted peaks were also found for one female and two immature individuals. It was likely that these δ15N-depleted peaks formed in early summer. The stable nitrogen isotope ratio (δ15N) values in Pacific saury (9.3 ± 1.4‰) did not differ significantly from that in Japanese anchovy (8.8 ± 0.9‰). In contrast, δ15N in krill (7.2 ± 0.5‰ in July and 8.0 ± 0.2‰ in September) were significantly lower than in the Pacific saury. Thus, these peaks may reflect the dietary change from krill to fishes in the feeding migration of the whales. Growth rate of the baleen plate was estimated to be 129 mm/y, and it appeared that a dietary record of about 1.4 years remained in the baleen plate. For two immature whales, the maximum value of δ15N occurred at the tip of baleen. This δ15N enrichment may possibly be useful for discriminating weanlings and older whales.  相似文献   

5.
Abstract –  Two modal size groups of sexually mature Arctic charr ( Salvelinus alpinus ) differing in shape and found at different depths in Lake Aigneau in the Canadian sub-Arctic are described and tested for genetic and ecological differentiation. Forms consisted of a small littoral resident, mean size 21.7 cm, and a large profundal resident, mean size 53.9 cm. Mitochondrial DNA analysis indicated that seven of eight haplotypes were diagnostic for either the littoral or profundal fish, with 66.6% of the variation being found within form groupings. Pairwise tests of microsatellite data indicated significant differences in nine of 12 loci and a significant difference between the forms across all tested loci. Molecular variation was partitioned to 84.1% within and 15.9% between forms and suggestive of either restricted interbreeding over time or different allopatric origins. Stable isotope signatures were also significantly different, with the profundal fish having higher δ13C and δ15N values than the littoral fish. Overlap and separation, respectively, in the range of form δ13C and δ15N signatures indicated that carbon was obtained from similar sources, but that forms fed at different trophic levels. Littoral fish relied on aquatic insects, predominantly chironomids. Profundal fish were largely piscivorous, including cannibalism. Predominantly empty stomachs and low per cent nitrogen muscle-tissue composition among profundal fish further indicated that the feeding activity was limited to the winter when ice-cover increases the density of available prey at depth. Results provide evidence of significant differences between the modal groups, with origins in both genetics and ecology.  相似文献   

6.
ABSTRACT: To quantify the contribution by cocultured animals to waste assimilation in an intensive shrimp farm in Thailand, the food web structures of the macrobenthos in a reservoir pond, a shrimp culture pond and water treatment ponds were examined using the stable C and N isotope ratio technique. Seawater for aquaculture was drawn from a creek, and stored in a reservoir pond, used for farming the banana prawn Fenneropenaeus merguiensis in culture ponds, and then recycled through treatment ponds where the green mussel Perna viridis was cultured to remove organic wastes discharged from the farming. The clam worm Nereididae sp. and the mud creeper Cerithideopsilla cingulata in the culture pond had δ 13C values of −21.0‰ and −18.4‰, respectively, suggesting that shrimp feed (mean δ 13C = −20.7‰) was the main food source for these species. The δ 13C analysis also suggested that sediments (−23.7‰) in the reservoir pond and particulate organic matter (POM) (−24.0‰) and/or sediments (−25.0‰) in the treatment pond supplied carbon for most macrobenthic animals. However, green mussels in the treatment pond had a mean δ 13C value of −20.5‰, suggesting that shrimp feed was the main food source for this species.  相似文献   

7.
ABSTRACT:   Carbon and nitrogen isotopic ratios in tissue of the bivalve corbicula ( Corbicula japonica ) and particulate organic matter (POM) were measured along a salinity gradient in the Kushida Estuary, Japan. The bivalve exhibited a gradual isotopic enrichment from the uppermost estuarine site (δ13C = −24.8‰ and δ15N = 8.6‰) to the marine site (δ13C = −16.1‰ and δ15N = 11.8‰). Using the concentration-weighted mixing model, the bivalves' food source is estimated from the isotope values for the bivalves and POM from terrestrial plants, marine phytoplankton and benthic microalgae. The results indicated that the contributions of benthic micro algae and phytoplankton were small, while terrestrial particulate matter is significantly important for the corbicula diet, although the contribution varies among sampling sites.  相似文献   

8.
Abstract— As a result of water turbulence effects on boundary layer diffusion resistance and carbon isotopic discrimination, the δ13C values (ratios of 13C: 12C) of attached algae may often overlap those of terrestrial plants, thereby making it impossible to distinguish between the relative importance of these two potential food sources for aquatic animals. The present study used a dual isotope approach (δ13C and δ15N) to refine measurements of the incorporation of allochthonous organic matter into freshwater fishes. The dependence of five species of littoral fishes on terrestrial detritus for part of their energy sustenance was demonstrated. The littoral zones of boreal Canadian Shield lakes are, therefore, not isolated from their surrounding riparian forests in terms of carbon flow as present day timber management guidelines erroneously assume, but instead exhibit a measurable degree of ecotonal land-water coupling. As a result, clearcut logging of riparian forests to the lakeshore edge, permissible by law in most Canadian provinces containing boreal forests, may have to be reassessed as a forest harvesting strategy.  相似文献   

9.
Stable carbon isotope ratios (δ13C) were used to estimate the relative contributions of natural and prepared feeds to the nutrition of golden shiners Notemigonus crysoleucas in ponds. Concurrent feeding trials were conducted in tanks (110 L) and ponds (0.04 ha) to determine the response of golden shiners to three isotopically distinct prepared diets both in the presence (pond) and absence (tank) of natural food. Seston was the primary indicator of the δ13C of natural foods available in the ponds, but δ13C's of free-swimming, unfed golden shiners provided an additional index. Fish receiving experimental diets were maintained in floating nets within the same ponds. After 6 wk, fish in tanks fed all three diets had acquired the diet label to some degree, while fish in ponds also tracked their respective feeds except for those fed diet 3. This diet contained a large amount of corn meal, which appeared to be poorly assimilated by golden shiners. The use of natural foods by golden shiners fed all three prepared feeds ranged from 40–83% and was inversely correlated with the relative assimilation of the prepared feeds.  相似文献   

10.
Abstract –  Many populations of vertebrates display alternative reproductive strategies involving delays in maturation processes and migrations to more productive habitats. Notably for females, migratory patterns and diet could influence reproductive traits such as ova size and number. To test this hypothesis, we targeted anadromous and freshwater-resident female brown trout of various sizes during their return to spawn in tributaries, and carried out stable isotope analyses (δ15N and δ13C) on ova to identify their feeding areas and diet. The study was performed in the Oir River (France), a small coastal system where trout migrations to sea and within the river basin have been monitored for the last 20 years. General trends were observed in reproductive traits, such as the positive correlation between female fork length, fecundity and ova size. Fecundity was size-dependent whatever the migratory origin of females, but major divergences were seen for ova size and isotopic ratios. Freshwater residents displayed a constant increase in ova size and a 15N-enrichment in ova, suggesting an investment in larger ova and a shift to piscivory as the fish become larger and older. Conversely, anadromous females had smaller ova compared with freshwater-resident females of similar body size and achieved higher fecundity as they grew bigger. Our results suggest the existence of a continuum of reproductive traits for freshwater-resident females whereas anadromous females clearly show a break with this continuum. This major dissimilarity could be explained by the difference in growing environments in terms of food availability and quality.  相似文献   

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