Mean Weight Of Stomach Contents Research Articles

Dietary overlap between the potential competitors herring, sprat and anchovy in the North Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 470:101-111 (2012) - DOI: https://doi.org/10.3354/meps09919 Dietary overlap between the potential competitors herring, sprat and anchovy in the North Sea K. Raab1,2, L. A. J. Nagelkerke2, C. Boerée1, A. D. Rijnsdorp1,2, A. Temming3, M. Dickey-Collas1 1Wageningen IMARES, PO Box 68, 1970 AB IJmuiden, The Netherlands 2Aquaculture and Fisheries Group, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands 3Institut für Hydrobiologie und Fischereiwissenschaft, Olbersweg 24, 22767 Hamburg, Germany *Email: kristina.raab@wur.nl ABSTRACT: European anchovy Engraulis encrasicolus increased its abundance and distribution in the North Sea during the mid-1990s and may consume similar zooplankton to and/or compete with other occupants of the North Sea like herring Clupea harengus and sprat Sprattus sprattus. The diets of adult anchovy, sprat and juvenile herring of comparable sizes, sampled close in time and space, were compared to understand how the 3 species prey on zooplankton and establish whether their diets overlap or not. Anchovy was found to be more generalist, consuming a higher diversity of prey items. Herring was more specialized, with low diversity of food items. Sprat was intermediate between anchovy and herring. The dietary overlap between anchovy and sprat was highest, followed by herring and sprat before anchovy and herring. The mean weight of stomach contents did not differ between species. We conclude that of the 3 species, anchovy is likely to be the least affected by changing plankton communities. KEY WORDS: Stomach analysis · Generalist · Specialist · Planktivorous fish Full text in pdf format PreviousNextCite this article as: Raab K, Nagelkerke LAJ, Boerée C, Rijnsdorp AD, Temming A, Dickey-Collas M (2012) Dietary overlap between the potential competitors herring, sprat and anchovy in the North Sea. Mar Ecol Prog Ser 470:101-111. https://doi.org/10.3354/meps09919 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 470. Online publication date: December 06, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Feeding habits of small-spotted catshark (Scyliorhinus canicula Linnaeus, 1758) from the eastern central Adriatic Sea

The feeding habits of small-spotted catshark, Scyliorhinus canicula, from the central Adriatic Sea, were investigated with respect to fish size, season and sampling location. Stomach contents of 1200 specimens, collected at monthly intervals (January to December 2010), were analysed. The prey items identified in the stomachs belonged to eight major groups: Cephalopoda, Polychaeta, Stomatopoda, Decapoda, Mysidacea, Euphausiacea, Amphipoda and Teleostei. Decapods were the most important ingested prey in all seasons, for medium sized fish (22–38 cm TL). Euphausiids and mysids constituted the main prey items of small fish (<22 cm TL) while teleosts dominated the stomach contents of larger specimens (>38 cm TL). Two decapods, Alpheus glaber (%IRI = 5.1) and Solenocera membranacea (%IRI = 3.0), were the most numerous prey items identified to species level. The mean weight of stomach contents (relative to predator size) increased significantly for fish larger than 30 cm TL, while the mean number of prey items did not differ significantly among size-classes. The percentage of empty stomachs showed a monthly variation with a maximal occurrence in February (48.0%) and a minimal in August (9.0%). The lowest feeding frequency could be related to low sea temperatures during the winter. The small-spotted catshark could be considered a generalistic predator.

Feeding habits of megrim,Lepidorhombus whiffiagonis(Walbaum, 1792), from the central Adriatic Sea

Summary The feeding habits of the megrim, Lepidorhombus whiffiagonis, from the central Adriatic Sea were investigated with respect to fish size and seasons. Stomach contents of 510 specimens, 9.0–28.9 cm total length (TL), collected by bottom-trawl from 2004 to 2006 were analyzed. The percentage of 97 empty stomachs varied significantly with season (maximum during the winter, 32.1%; minimum during summer, 7.4%). The food composition suggests that the megrim is a carnivorous fish. Prey items identified in the stomachs belong to four major groups: Teleostei, Decapoda, Mysidacea and Cephalopoda. Teleosts were the most important (%IRI = 82.2), especially in fish larger than 14 cm TL. Mysidacea constituted the main prey for fish less than 14 cm TL. At the species level, the teleost Antonogadus megalokynodon (%IRI = 1.5) and decapod Processa canaliculata (%IRI = 0.9) were the most frequent prey. The mean weight of stomach contents increased significantly for fish larger than 14 cm TL, while the mean number of prey items did not differ significantly among size classes. Diet composition showed little seasonal variation; teleosts were the most important prey in all seasons, especially during spring. The lowest intensity of feeding recorded in winter could be related to the lower sea temperature and to the spawning period.

Feeding habits of horse mackerel, Trachurus trachurus (Linneaus, 1758), from the central Adriatic Sea

Summary The feeding habits of the horse mackerel, Trachurus trachurus, from the central Adriatic Sea were investigated with respect to fish size and season. Stomach contents of 1200 specimens 12.9–37.6 cm total length (TL) taken at monthly intervals (January–December 1995) were analyzed. Of the total number of stomachs examined, 597 were empty (49.7%). This percentage varied significantly with season; the maximum number of empty stomachs was observed during January (80%) and February (82%) and a minimum number observed during July (15%) and August (19%). A total of 30 different prey species belonging to five major groups: Crustacea (Euphausiacea, Mysidacea, Decapoda), Cephalopoda, and Teleostei was identified in the stomach contents. Euphausiids were the most important ingested prey in all seasons as well as in small- and medium-size classes ( 30 cm TL individuals. The mean weight of stomach contents increased significantly for fish larger than 24.1 cm TL, while the mean number of prey items significantly declined in the large-size classes.

Age, Growth and Feeding Habits of the Brown ComberSerranus hepatus(Linnaeus, 1758) on the Cretan Shelf

Forty-five samples of the brown comberSerranus hepatuswere collected during experimental surveys carried out on a monthly basis (August 1990 to August 1992) along the Cretan continental shelf. A total of 1268 specimens 31–140mm in total length were analysed. Growth was well described by both standard and seasonalized forms of the von Bertalanffy growth model and the computed parameters wereL∞;=152mm,k=0·36,t0=−0·57. Feeding intensity was high throughout the study period and varied significantly among the age classes of fish examined. Stomach content analysis revealed thatS. hepatusis carnivorous, feeding mainly on decapods. Diets did not vary seasonally; decapods were the most important prey throughout the year. However, the composition of the prey consumed varied considerably with predator age coupled with differences in mean prey sizes utilized by each age class. The mean weight of stomach contents increased significantly for older specimens, while the mean number of prey items decreased. Age-specific dietary selection was primarily a function of body size of the predator and appears to reduce intra-specific competition among the members of the different age classes. The results suggest thatS. hepatusplays an important trophic role as a macrophagic carnivorous species on the Cretan continental shelf.

Effects of rearing technique and fish size on post‐stocking feeding, growth and survival of European grayling, Thymallus thymallus (L.)

European grayling, Thymallus thymallus (L.), were reared by four different techniques: (A) in a natural pond without a supply of artificial diet; (B) in a net pen fed artificial dry diet; (C) in tanks fed artificial dry diet; (D) in tanks, and for 16 days before stocking, transferred to a diet based on mixed frozen natural food exclusively. Fish within groups C and D were also split into subgroups of large and small fish. Feeding, growth and survival of fish in the different groups were compared after stocking into three different stocking sites during the spring of 1994. The stocking sites consisted of a barren lake (Lake L), a second lake (Lake N) containing an allopatric perch, Perca fluviatilis L., population, and a barren man‐made pond. In Lake L, higher recapture rates and mean weights of stomach contents were obtained in fish reared in the natural pond and in the net pen. There were no differences in total recapture rate, or mean condition factor between small and large fish within groups C and D. In Lake N only five (0.5%) stocked grayling from rearing groups A and B were recaptured during the experiment and more fish from categories C and D were recaptured. This was probably related to size‐selective predation. In the pond, there were no differences in recapture rates or in mean weight of stomach contents between fish from any of the groups. In sample 1 (Lake N, 22 days after stocking), mean weight of stomach contents was higher in the larger fish within categories C and D but there was no difference in condition factor between the groups. In sample 1, mean condition factor of fish from the different groups varied markedly, being highest in Lake L followed by Lake N and the Pond. Fourteen out of 26 dead fish in the pond showed clinical symptoms of the bacterial disease ASA. Mortality was related to low initial condition factor at the time of stocking. No stocked grayling were recaptured from the two lakes in the last sample (June 1995).

Feeding habits and ontogenetic diet shift of the striped red mullet, Mullus surmuletus Linnaeus, 1758

The feeding habits of the striped red mullet, Mullus surmuletus on the Cretan shelf (north-eastern Mediterranean), in respect to season and fish size, were examined. Stomach contents of 446 specimens, 62–230 mm TL, collected by demersal trawl from August 1988 to August 1989, were analyzed. Feeding intensity was high throughout the study period and varied significantly among the size classes. Crustaceans (amphipods and decapods) predominated M. surmuletus diet. The composition of the prey ingested varied with predator size fish and cephalopods occurred exclusively in the diet of specimens larger than 161 mm TL. The mean weight of stomach contents increased significantly for fish larger than 171 mm TL, while the mean number of prey items did not differ among the size classes. Diets varied seasonally; decapods were more important in summer, whereas amphipods were more important during winter and spring. The results indicated that the red striped mullet fed on a narrow range of prey items and could be considered a specialist. The morphological characteristics and the foraging behaviour of M. surmuletus account for both prey type selection and the feeding patterns observed.

Comparative analysis of stomach contents of cultured and wild cod, Gadus morhua L.

In a cod enhancement project in a small fjord in western Norway, two groups of reared cod, Gadus morhua L., were released with 6 months’difference in time. After the last release a 3-week fishing survey was conducted. Stomachs from wild and recaptured reared cod of similar size were sampled and analysed. The last released cod had learned to catch the same prey types and in the same relative proportions as the wild cod the second week after release, but mean weight of stomach contents and mean numbers of prey items per stomach were smaller, and a larger proportion of the newly released fish had empty stomachs. Three weeks after release the proportion of empty stomachs was similar to that of wild cod and the first released reared cod, but the food intake was still smaller. The first released group of reared cod, which had spent 6 months in the fjord, seemed to feed as efficiently on wild prey as did wild cod.

Effect of water temperature on stomach evacuation rates, and estimation of daily food intake of bluegill sunfish (Lepomis macrochirus Rafinesque)

Field experiments were conducted over the summer of 1983 to determine food-evacuation rate and measure stomach fullness of bluegill sunfish (Lepomis macrochirus). A combination of these data gave estimates of daily food intake of fish. Fish were captured and held in large holding pens in Lake Opinicon, Ontario, Canada, and periodically subsampled over 24 h to monitor changes in mean weight of stomach contents. Stomach-evacuation rates obtained in this way increased significantly with water temperature over the range 10–25 °C. However, variation in stomach-evacuation rate was considerable, reducing the utility of water temperature as a predictor of stomach-evacuation rate. It is suggested that the simple field methods employed here to estimate stomach evacuation and food intake are more useful in the estimation of daily ration than the more commonly employed laboratory-based methods.

Daily rations, diel feeding activity and distribution of age-0 brook charr, Salvelinus fontinalis, in two subarctic streams

Diel variations in the stomach content weight of age-0 brook charr indicate that they fed primarily during the day in Matamek River and Riviere a la Truite, Quebec. Age-0 charr in both rivers moved close to the shore at night. The mean weight of stomach contents in Riviere a la Truite was highest at the end of the daylight period, whereas in the Matamek River stomach content weights maintained maximum level during most of the day, except in August when high water temperatures reduced food intake. Daily rations were estimated at 5.09 and 4.09% body weight for charr from Riviere a la Truite in July and August, respectively. In the Matamek River, estimates were 7.13, 9.75, and 1.27%, in June, July, and August, respectively. Charr from Matamek River had a higher instantaneous growth rate than charr in Riviere a la Truite (3.96 versus 2.72% body weight per day) and were significantly heavier by mid-August. Differences observed between populations in daily rations and growth rates were attributed mainly to differences in water temperature regimes.

Seasonal diets of mooneye, Hiodon tergisus, in the Assiniboine River

Stomach analyses of 665 mooneye (Hiodon tergisus) netted from the Assiniboine River during a 12-month period indicate that mooneye fed mainly on insects. Corixids occurred in about 80% of the stomachs that contained food and formed the bulk of the ingesta. Other insects eaten were coleopterans, ephemeropterans, dipterans, odonatans, plecopterans, and hymenopterans. Amphipods, crayfish, and plant materials were other items taken.Mooneye fed during each month of the year but vernal (April–June) and autumnal (September–November) peaks occurred. There were significant seasonal variations in percentages of stomachs with food and in the mean weight of stomach contents. Monthly mean food weights were significantly greater for adult male mooneye during the autumnal peak.