This investigation was supported in part through research grants from the Environment Agency (Sussex Area) and the UK Department of Environment, Food and Rural Affairs, the Spanish Ministry of Education and Science (REN2003-00477), the
Government of Catalonia (Distinction Award for University Research 2004 to EGB) and the EC Marie Curie programme

Voracious invader or benign feline? A review of the environmental biology of European catfish Silurus glanis in its native and introduced ranges

Effect of temperature and feeding frequency on growth performances, feed efficiency and body composition of pikeperch juveniles (Sander lucioperca).

The effects of industrial cooling water on fish communities were widely debated at the end of the seventies, when large thermal power plants were being developed. This led to numerous research programs on thermal tolerance in fish. The recent warming climatic period and especially the 2003 heat wave have brought thermal biology back to center stage. The work presentedherehasconsistedinanalyzinghistoricalandcontemporaryliterature to update basic knowledge on thermal tolerances of 19 riverine fish species. These data were then validated and completed by European fish specialists. We finally proposed a synthesis, based on more than 300 references, which details thermal tolerances for the entire life cycle: reproduction, embryonic, larval, juvenile and adult life stages. This updated material is of great importance to an understanding of the trends observed in fish communitiesorforforecastingfuturebehaviorinclimatechangescenarios.

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Synthesis of thermal tolerances of the common freshwater fish species in large Western Europe rivers

– The size structure of a predator population can cause differences in the relative survival of different prey length classes whereby the biggest prey may reach a safe size because of the size-dependent character of predation. In the present study, the diet of European catfish was investigated to examine if catfish feeding can prevent cyprinids from reaching such a size refuge. In the lake studied, catfish was stocked for biomanipulation purposes to reduce unwanted roach and bream populations. Crayfish and roach were the most important prey items of catfish. If only species composition in the diet was considered, no clear changes were recorded in relation to catfish size. However, the length of roach as prey significantly increased with catfish length. Catfish were significantly larger than the other piscivorous fish in the lake, but took relatively smaller roach in comparison with similar-sized pike or pikeperch. Nevertheless, because of the high mean length of catfish, roach cannot reach a size refuge. For unknown reasons, the expected and intended predation on bream was not observed. Catfish took smaller prey than could be expected from mouth gape data. By extending the relationship between catfish as predator and roach as prey beyond the predator length range currently found in the lake, it could be shown that even catfish of 150 cm length will probably feed upon only 65% of all available bream length classes. Therefore, stocking with catfish cannot prevent a size refuge for the bream.

Can feeding of European catfish prevent cyprinids from reaching a size refuge

This study was conducted to investigate the effect of different water temperature ranges on growth performance, total length and feed conversion ratio of Labeo rohita. The three temperature ranges were 2022, 22-24 and 24-26°C. Two replicates were followed for each water temperature range. The feed was offered at the rate of 4% of wet body weight of the fish twice a day. Labeo rohita attained significantly higher body weight (11.650 ± 0.212g) and total length (10.485 ± 0.191 cm) under water temperature range of 24-26°C. This was followed by 10.803 ± 0.003g body weight and 9.720 ± 0.003 cm total length under water temperature range of 22-24 o C and 10.356 ± 0.062g and 9.335 ± 0.078 cm for body weight and total length respectively for the water temperature range of 20-22°C. The fish reared in water having temperature between 24-26°C showed the best FCR value (2.270 ± 0.059), followed by those maintained in 22-24°C (2.680 ± 0.146) and 20-22°C (2.970 ± 0.073). It was concluded that water temperature ranging from 24-26°C seemed to be the most effective for rearing of Labeo rohita.

Effect of water temperature on the growth performance and feed conversion ratio of Labeo rohita.

Summary

The influence of temperature on growth, feed conversion, and protein and gross energy utilization was assessed in two experiments using the European catfish, Silurus glanis L. Animals of 55 g and 24 g were used in trials lasting 6 and 7 weeks, respectively. The optimum temperature for growth was within the range of 25 to 28°C, with the best results obtained at 27°C. Using a feed of low protein content (30.3%), a feed conversion of 1.67 was achieved at a specific growth rate of 1.78% of body weight/day.

V. Hilge

Papers

The influence of temperature on the growth of the European catfish (Silurus glanis L.)