Barry, Terence P.; Malison, Jeffrey A. (ed.) / Proceedings of PERCIS III, the Third International Percid Fish Symposium, University of Wisconsin, Madison, Wisconsin, U.S.A., July 20-24, 2003
Matěna, Josef, et al.
(General biology) Distribution of young-of-the-year percids in European reservoirs, pp. 109-110 PDF (1.1 MB)
DISTRIBUTION OF YOUNG-OF-THE-YEAR PERCIDS IN EUROPEAN RESERVOIRS Matena Josef, tech Martin, Drastik Vladislav, Frouzovi Jaroslava, Kratochvil Michal, Kubecka Jan, Peterka Jifi, Vagek Mojmir. Hydrobiological Institute, Academy of Sciences, Na sidkach 7, and Biological Faculty USB, Branisovskd 31, 37005 Cesk6 Budejovice, Czech Republic. matena(hbu.cas.cz. Introduction. Besides the cyprinids, perciform fish are the most successful in colonizing European reservoirs. This paper summarizes numerous published and unpublished information on perch (Perca fluviatilis), pike perch (Sander lucioperca) and ruffe (Gymnocephalus cernuus) distribution and behavior during the first year of life. The emphasis is given on the aspects of biology not mentioned in Urho (1996) and Craig (2000). Methods. Open water of five Czech reservoirs was sampled by ichthyoplankton towed nets (Wanzenbock et al., 1997; May-July), by 3*3 m frame trawl (August- September) and by the SIMRAD EY 500 split-beam echosounder. Littoral regions were sampled using fry beach seine (10 m long, mesh size 1*1.35 mm). All samplings were performed either during day time or during 24 hours. All fish were counted and measured to the nearest 0.5 mm. The results from three non- stratified drinking water reservoirs in the Meuse estuary, the Netherlands (Kube~ka et al., 1998) are used for comparison. Results and Discussion. J.Spawning, hatching and embryonic period. The trigger of perch spawning is the onset of thermal stratification when the surface temperature reaches 80C (second half of April). The spawning is one continuous event lasting about one month with most activity at depth strata corresponding to 8-12'C (Pivni~ka and 9vatora, 2001). Pikeperch and ruffe spawn slightly later. Especially the spawning of ruffe can be prolonged during May to July. The spawning of pikeperch is usually considered as a single event, but the appearance of very small (15-25 mm) fry in August amongst contemporaries 50-150 mm long may indicate portional spawning in Dutch reservoirs. 2. Pelagic larval period. Marine origin of percids predetermined pelagic phase in the life cycle. 2.1. Surface-confined period. Larvae of perch and pikeperch are positively phototactic. They leave spawning grounds, enter open water and inhabit surface layers during the day (Fig. 1) for week or two (length 5-10 mm, end of May). Unpublished acoustic studies show that in this period schooling aggregations are missing (randomly distributed ichthyoplankton). This period seems to be present in all studies compared and the larvae seem to avoid littoral. 2.2. Period of more diverse distribution. In subsequent period, social contacts and schooling develops gradually, the behavior of larvae splits in several modes: 0 0 2 _-- I a 61 8 1 % of total abundance I 10 20 30 40 50 60 70 -i-X~~~~~t ,,..... . ....... -. A I I - - Lipno Perch - Klicava Perch -*-- Rimov Perch I | X Lipno Pikeperch I I Figure 1. Vertical distribution of percid fiy during surface-confined period (end of May, day time). %of total abundance 0 10 20 2 4 6 8 10 12 14 16 30 Figure 2. Vertical distribution of percid fry during the period of bimodal distribution (day time, 0700-1900). a) Surface distribution like in 2.1. This type of distribution is often reported in the literature, but it was never encountered during our studies when all types of habitats were sampled. Such references have to be treated with caution, as they may be result of undersampling of deep pelagics. Pavlov et al. (1988) show preference of pikeperch to the surface layers. b) Bimodal vertical distribution with epi- and bathy- pelagic perciform fry (Fig. 2). This type is typical for deep stratified reservoirs. The cohort of all three species splits into differently behaving groups: Epipelagic fry (EPF), which spends the whole 24 hours in upper 4 meters together with the fry of cyprinids and Bathypelagic fry (BPF) spending the day in hypolimnion at depths 10-20 m with no measurable light. No cyprinids are present in BPF. BPF formate 2- 3 m thick scattering layer, which can be followed by the echosounders. In the evening, these fish migrate to 109 A
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