Energy Costs of Catfish Space Use as Determined by Biotelemetry

Citation: Slavk O, Horky P, Zavorka L ( Energy Costs of Catfish Space Use as Determined by Biotelemetry Ondrej Slavk 0 Pavel Horky 0 Libor Za vorka 0 Adam J. Munn, The University of Wollongong, Australia 0 1 Department of Zoology and Fisheries, Faculty of Agrobiology , Food and Natural Resources , Czech University of Life Sciences Prague , Prague , Czech Republic , 2 Department of Zoology, University of Gothenburg , Go teborg , Sweden Animals use dispersed resources within their home range (HR) during regular day-to-day activities. The high-quality area intensively used by an individual, where critical resources are concentrated, has been designated as the core area (CA). This study aimed to describe how animals utilize energy in the HR and CA assuming that changes would occur according to the size of the used areas. We observed energetic costs of space use in the largest European freshwater predator catfish, Silurus glanis, using physiological sensors. Catfish consumed significantly more energy within the CA compared to the rest of the HR area. In addition, energetic costs of space use within a large area were lower. These results generally indicate that utilization of larger areas is related to less demanding activities, such as patrolling and searching for new resources and mates. In contrast, fish occurrence in small areas appears to be related to energetically demanding use of spatially limited resources. - The size of the home range (HR) used by animals during regular day-to-day activities [1] to satisfy their energy needs depends on the quality and availability of resources. Animals search for dispersed resources throughout the HR [2], the size of which can be larger than predicted by energy needs [3,4] reflecting, for example, low habitat productivity, in which the energy needs of the resident animals are poorly satisfied [5,6], and/or competition with neighbors for resources within the HR [79]. An unbalanced distribution of resources within the HR results in a disproportional use of the HR [10]. The preferred area of intensive use [11] or the most concentrated [12,13] within the HR is referred to as the core area (CA) [14] and is where individuals spend most of their time[15]. The CA contains critical resources for species [16], representing the highest quality environment [17] and ensuring the best fitness for residents [18]. The size of the CA and HR are mutually correlated, and both areas display an inverse relationship with available food resources [19]. The CA is frequently reported as the most important part of the HR [17,15]; thus, we assumed that an important amount of energy spent by an individual would occur within the CA and that the changes in energetics would occur according to the size of the used areas. To test our assumptions, we used the radio biotelemetry method. Specimens of the European catfish Silurus glanis (L. 1758), a large freshwater predator, were equipped with physiological sensors measuring energetics of an individual [20]. The correlation between electromyogram (hereafter EMG) records and animal behavior including fish is well documented [20]. EMG records were used to describe the movement activity of fish [21], reproductive behavior [22], a relationship between density and energetic expenditures of individuals in aquaculture [23], parental care [24], stress during transport [25], territorial defense [26] or contact between familiar and unfamiliar individuals [27]. The catfish can achieve a body weight of more than 100 kg [28], hunt aquatic and terrestrial vertebrates [29] and display individually characteristic energy costs of movement activity [30]. The catfish was chosen for the study because they show high site fidelity [31] enabling to determine the HR and CA of specimens [26]. Materials and Methods a) Study area The study was conducted on the Berounka and Elbe Rivers in the Czech Republic. The study sites were located in stretches of river characterized as lowland rivers with a gradual slope. These particular sites were chosen because of native catfish occurrence. A detailed description of the study sites can be found in [32] and [26] for the Berounka River (the river stretch studied was 3.5 km long; 49u559N; 14u149E; 49u569N; 14u179E) and the Elbe River (the river stretch studied was 20 km long; 50u099N; 15u489E; 50u029N; 15u469E), respectively. No special permit is required for the field work; the species is not protected by legislation in force. The observation was announced to competent authorities that were: Elbe River Authority and Vltava River Authority, River Management Authorities, state enterprises, and to Czech Anglers Club, civic association, Fish Management Authority. b) Fish capture and tagging A total of 20 individuals (16 from the Berounka River and four from the Elbe River) were captured through electrofishing (650 V, GM .19 .584 .42 .185 .68 .317 .217 .92 .563 .221 .063 .07 .552 .56 .641 .228 .27 .94 .44 .943 E 8 1 6 1 7 1 1 4 1 1 2 7 1 4 2 1 5 5 6 1 9 8 7 4 8 3 5 2 1 1 7 GM .29 .59 .03 .9 88 .35 .1 59 .56 .4 .09 .13 .2 55 .69 .2 17 .11 .27 .46 1 . 2 . 1 6 . 2 . E 8 1 6 1 7 1 1 4 1 1 2 7 1 4 2 1 6 6 7 1 (m 3 4 3 3 0 A 55 06 43 51 73 05 42 20 02 73 79 95 87 21 40 23 01 40 65 48 C 7 9 2 4 2 2 2 3 1 6 4 7 2 6 1 9 4 2 4 1 a a a a a a a a a a a a a a a a k k k k k k k k k k k k k k k k n n n n n n n n n n n n n n n n r u u u u u u u u u u u u u u u u ev ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro ro e e e e i e e e e e e e e e e e e e e e e lb lb lb lb R B B B B B B B B B B B B B B B B E E E E 1 u n 2 8 5 1 7 7 6 4 2 8 6 2 5 4 1 3 5 8 2 9 e .3 .9 .0 .3 .8 .0 .3 .6 .4 .9 .1 .1 .2 .4 .7 .8 .8 .2 .6 .3 L 1 0 1 1 0 1 1 1 1 1 2 1 1 1 1 0 0 1 1 1 4 A, pulsed DC). The surgery was performed under 2-phenoxy ethanol (0.2 ml l2l; Merck KGaA; www.merck.com) and all efforts were made to minimize suffering. The fish were weighed and measured (Table 1). The mean weight and length of the captured fish were 20.5 kg (range: 5.564.5 kg) and 1.34 m (range: 0.83 2.16 m) for the Berounka River and 17.5 kg (range: 4.428.5 kg) and 1.29 m (range: 0.851.62 m) for the Elbe River. Electromyogram (EMG) transmitters (CEMG2R1125, mass 12 g in air, 11.49 mm, with an operational life of c. 71 days; Lotek; www. lotek.com) were implanted in the body cavity of each fish through a mid-ventral incision that was closed by three separate stitches using a sterile braided absorbable suture (Ethicon coated VICRYL). The two electrodes of the surgically implanted EMG transmitters were positioned in the red aerobic musculature below the lateral line on the left side of the fish. The distance between the electrodes ranged from 10 to 12 mm [33]. The individuals equipped with the EMG transmitters were kept in cages immersed in the river stretch for c. 60 min after implantation of the transmitters. They were then released at or near the point of capture. c) Sampling procedures The fish were monitored from 1 March to 31 May 2006 (Elbe River) and (...truncated)