An assessment of post-plague reintroduced native white-clawed crayfish, a Ustropotamobius pallipes, in the Sherston Avon and Tetbury Avon, Wiltshire

This article reports on the success of reintroducing native crayfish (Austropotamobius pallipes) in the Sherston and Tetbury Avon, following extinction of the population from crayfish plague. The authors describe and review the survey methods that were used and identify a survey technique that was found to be the most rapid and robust for monitoring crayfish populations. Such a survey technique could be adopted as a standard method.

Observations on the behaviour of Polyphemus pediculus and functions of its extremities in the process of feeding. [Translation of: Materialy po biologii i gidrologii Volzhskikh vodokhranilishch, pp. 13-16. Moscow, 1965]

The author summarises observations on the behaviour of Polyphemus pediculus and functions of its extremities in the process of feeding. The crustacean Polyphemus pediculus seizes its prey, kills it and pulverises its food with the help of its extremities. Therefore for a study of its feeding method was necessary not only to have been acquainted in detail with the structure of its extremities, but also to have observed their interaction for the accomplishment of the stated functions.

Quantitative data on the feeding of Cyclops strenuus Fischer and Cyclops viridis Jurine. [Translation from: Trudy saratov.Otd.vses.nauchno-issled.Inst.ozer.rech.ryb.Khoz. 1, 163-176, 1951.]

Cyclopids, exactly in the same way as daphnids, significant component in the nutrition of plankton-f and the young of the majority of fishes. It is established that the food spectrum of cyclopids is extremely broad: daphnids, planarians, Copepodite stages of copepods (cannibalism), rotifers, protists, bacteria, phytoplankton and so on. It is clear that the problem of studying these or other components of feeding in the general food spectrum can be definitely resolved only after obtaining exact quantitative data on the feeding of cyclopids. This article attempts to fill the gap in the study of the quantitative side of the feeding of cyclopias; in it is investigated the size of the 24-hour ration of cyclopids feeding on protists, the dependence of the ration on some factors of the external medium, and the difference of 24-hour consumption per unit weight of tody with two species of cyclopids (Cyclops strenuus and Cyclops viridis).

Behaviour and mechanism of feeding of Lathonura rectirostris (Cladocera, Macrothricidae). [Translation from: Zoologicheskie Zhurnal 50, 1002-1010, 1971.]

The behaviour in the feeding process and the functional morphology of Lathonura rectirostris O.F. Muller - one of the widely distributed species of macrothricids - is studied. The current work is an attempt at morpho-functional analysis of the apparatus of the trunk appendages of Lathonura rectirostris O.F. Muller. This highly specialized species, the method of feeding of which basically comes to the mechanical scraping-off and collection of epiphytic single-celled algae and particles deposited on the surface of aquatic plants.

Investigations of certain eco-physiological characteristics of the broad and long-pincered crayfish in connection with their interspecific relationships. [Translation from: Lietuvas TSR Mokslu Akademijos Darbai, C Serija 2(40), 279-286, 1966.]

The results are described of eco-physiological investigations of the broad-pincered (Astacus astacus L.J.) crayfish and the long-pincered (Astacus astacus Esch.) crayfish, conducted in 1963—64 in the Institute of Zoology and Parasitology of the Academy of Science of the Lithuanian SSR, for the purpose of studying the interspecific relationship of these two species. In the course of the investigation were determined: the influence of the temperature of the environment on the consumption of oxygen by full grown individuals of both species and on the respiratory movements of the scaphognathites, the threshold temperatures and the saturation of the water by oxygen, the diel activity in the winter period.

Growth and reproduction of Moina rectirostris (Leydig) and Ceriodaphnia quadrangula (O. F. Muller) with feeding on detritus. [Translation from: Sbornik po prudovomu rybovodstvu, 79-89. Moscow, VNIRO, 1969.]

The significance of detritus in the nutrition of aquatic animals, especially of the small representatives of the zooplankton, has been studied very slightly. Research so far has established that in M. rectirostris with feeding on protococcal and single-celled green algae and bacteria the beginning of formation of eggs takes place in 2 - 4 days. The young appear in 4 - 6 days. In this study M. rectirostris and C. quadrangula are fed on detritus of natural origin in laboratory conditions. In order to determine the assimilability and productive: effect of detritus, the author set up experiments, permitting to characterize the rate of growth, speed of maturing and fertility of M. rectirostris and C. quadrangula with feeding of them on detritus of different composition and age.

Comparative feeding ecology of two elasmobranch species, Squalus blainville and Scyliorhinus canicula, off the coast of Portugal

The small-spotted catshark (Scyliorhinus canicula) (Linnaeus, 1758) and the longnose spurdog (Squalus blainville) (Risso, 1826) are two species occurring in the European and western African continental shelves with a wide geographical distribution. In this study, the diet of S. blainville and S. canicula off the Portuguese western Atlantic coast was investigated in 2006 by collecting monthly samples of these two species from local fishing vessels. In the stomachs of both species, crustaceans and teleosts were the dominant prey items, and molluscs, polychaetes, echinoderms, and sipunculids were found in lower abundance. In S. canicula, urochordate and chondrichthyan species were also observed in stomachs and were classified as accidental prey items. Scyliorhinus canicula consumed a broader group of prey items than did S. blainville. A significant diet overlap was observed, despite both species occupying different depth ranges over the continental shelf. Scyliorhinus canicula exhibited a consistency in diet composition among seasons, sexes, and maturity stages. Nonetheless, for both adults and juveniles, an increase in relative abundance of teleosts in the diet was observed in the spring and summer. This study provides evidence of the importance of S. canicula and S. blainville as benthic and pelagic predators along the western Atlantic coast.

Feeding ecology of juvenile Pacific salmon (Oncorhynchus spp.) in a northeast Pacific fjord: diet, availability of zooplankton, selectivity for prey, and potential competition for prey resources

We investigated the feeding ecology of juvenile salmon during the critical early life-history stage of transition from shallow to deep marine waters by sampling two stations (190 m and 60 m deep) in a northeast Pacific fjord (Dabob Bay, WA) between May 1985 and October 1987. Four species of Pacific salmon—Oncorhynchus keta (chum) , O. tshawytscha (Chinook), O. gorbuscha (pink), and O. kisutch (coho)—were examined for stomach contents. Diets of these fishes varied temporally, spatially, and between species, but were dominated by insects, euphausiids, and decapod larvae. Zooplankton assemblages and dry weights differed between stations, and less so between years. Salmon often demonstrated strongly positive or negative selection for specific prey types: copepods were far more abundant in the zooplankton than in the diet, whereas Insecta, Araneae, Cephalapoda, Teleostei, and Ctenophora were more abundant in the diet than in the plankton. Overall diet overlap was highest for Chinook and coho salmon (mean=77.9%)—species that seldom were found together. Chum and Chinook salmon were found together the most frequently, but diet overlap was lower (38.8%) and zooplankton biomass was not correlated with their gut fullness (%body weight). Thus, despite occasional occurrences of significant diet overlap between salmon species, our results indicate that interspecific competition among juvenile salmon does not occur in Dabob Bay.

Feeding ecology of Atlantic bluefin tuna (Thunnus thynnus) in North Carolina: diet, daily ration, and consumption of Atlantic menhaden (Brevoortia tyrannus)

Diet, gastric evacuation rates, daily ration, and population-level prey demand of bluefin tuna (Thunnus thynnus) were estimated in the continental shelf waters off North Carolina. Bluefin tuna stomachs were collected from commercial fishermen during the late fall and winter months of 2003–04, 2004–05, and 2005–06. Diel patterns in mean gut fullness values were used to estimate gastric evacuation rates. Daily ration determined from mean gut fullness values and gastric evacuation rates was used, along with bluefin tuna population size and residency times, to estimate population-level consumption by bluefin tuna on Atlantic menhaden (Brevoortia tyrannus). Bluefin tuna diet (n= 448) was dominated by Atlantic menhaden; other teleosts, portunid crabs, and squid were of mostly minor importance. The time required to empty the stomach after peak gut fullness was estimated to be ~20 hours. Daily ration estimates were approximately 2% of body weight per day. At current western Atlantic population levels, bluefin tuna predation on Atlantic menhaden is minimal compared to predation by other known predators and the numbers taken in commercial harvest. Bluefin tuna appear to occupy coastal waters in North Carolina during winter to prey upon Atlantic menhaden. Thus, changes in the Atlantic menhaden stock status or distribution would alter the winter foraging locations of bluefin

The repulsive and feeding-deterrent effects of electropositive metals on juvenile sandbar sharks (Carcharhinus plumbeus)

Reducing shark bycatch and depredation (i.e., damage caused by sharks to gear, bait, and desired fish species) in pelagic longline fisheries targeting tunas and swordfish is a priority. Electropositive metals (i.e., a mixture of the lanthanide elements lanthanum, cerium, neodymium, and praseodymium) have been shown to deter spiny dogfish (Squalus acanthias, primarily a coastal species) from attacking bait, presumably because of interactions with the electroreceptive system of this shark. We undertook to determine the possible effectiveness of electropositive metals for reducing the interactions of pelagic sharks with longline gear, using sandbar sharks (Carcharhinus plumbeus, family Carcharhinidae) as a model species. The presence of electropositive metal deterred feeding in groups of juvenile sandbar sharks and altered the swimming patterns of individuals in the absence of food motivation (these individuals generally avoided approaching electropositive metal closer than ~100 cm). The former effect was relatively short-lived however; primarily (we assume) because competition with other individuals increased feeding motivation. In field trials with bottom longline gear, electropositive metal placed within ~10 cm of the hooks reduced the catch of sandbar sharks by approximately two thirds, compared to the catch on hooks in the proximity of plastic pieces of similar dimensions. Electropositive metals therefore appear to have the potential to reduce shark interactions in pelagic longline fisheries, although the optimal mass, shape, composition, and distance to baited hooks remain to be determined.

Reducing feed costs in semi-intensive finfish culture: an update on mixed feeding schedules and an idea for enhancing endogenous food supply in ponds

Some interesting ideas on improving the cost-effectiveness of feeding in semi-intensive finfish aquaculture are presented.

Diet and feeding ecology of two sizes of Barbodes gonionotus (=Puntius gonionotus) and Oreochromis sp. in ricefields in Bangladesh

Fish culture experiments were conducted to compare and evaluate the feeding pattern and strategies, daily ration, gastric evacuation rates, dietary breadth, similarity and overlap of silver barb, Barbodes gonionotus, and tilapia, Oreochromis sp. (natural hybrid of O. mossambicus x O. niloticus) in a rice-fish system. B. gonionotus was found to be a macrophtophagous column feeder while Oreochromis sp. was a detrivorous benthophagic browser. Ontogenic shifts in diet were clearly observed in B. gonionotus while absent in Oreochromis sp. For both species, daily food ration for the small fish was twice as large as that for the large fish. Mean rates of gastric evacuation were 0.18 h super(1) for small and 0.05 h super(1) for large B. gonionotus and 0.09 h super(1) and 0.14h super(1) for small and large Oreochromis sp., respectively. In terms of intraspecific dietary width, the smaller sized individuals of both species had a wider dietary niche than the larger conspecifics. Larger fish increased their specialization and reliance on few food items with increasing size and competitive ability. When both species were reared together, B. gonionotus showed a wider niche width than tilapia. Wider interspecific niche width of B. gonionotus compared to that of tilapia and significant interspecific dietary overlap is likely to result in suppression of the growth of tilapia in mixed culture due to: 1) a high degree of specialization and reliance of tilapia on food of low-nutrient value, and 2) slower gastric evacuation rates as compared to B. gonionotus, which would allow B. gonionotus to outgrow similar sized tilapia.

Food and feeding habits of Synodontis nigrita from the Osun River, SW Nigeria

An investigation was conducted into the food and feeding habits of Synodontis nigrita from the Osun River near Epe, Lagos, Nigeria. The food items in the stomach of the S. nigrita covered a wide spectrum, ranging from various types of plankton to invertebrates and plants. A seasonal variation was also noted in the stomach contents of S. nigrita over the period of investigation. The predominant food items found in the stomach were Polycystis spp., Closterium spp., Oedogonium spp., plant tissues, insect parts and detritus. This suggests that S. nigrita is an omnivore.

A preliminary study on the feeding regime of European pilchard (Sardina pilchardus Walbaum 1792) in Izmir Bay, Turkey, Eastern Aegean Sea

The gut contents of Sardina pilchardus specimens captured in Izmir Bay were examined in order to determine their feeding regimes. Of the 365 stomachs examined, 321 (87.95%) contained food and 44 (12.05%) were empty. Analysis of gut contents verified that S. pilchardus feeds on zooplankton. The most important group in the diet of S. pilchardus was copepods (79.79%). Decapod crustacean larvae (8.17%) and bivalves (3.18%) were second and third, respectively, in order of importance. The application of analysis of variance to monthly data of numerical percentage, weight percentage, frequency of occurrence and index of relative importance indicated that there was no significant difference between months. Oncaea media was the most dominant species for six months of the year. Euterpina acutifrons, Centropages typicus, Calanoida, Oncaea sp. and Corycaeus sp. were the most dominant for March, April, May, September, October and December.