Diet and growth of asp, Aspius aspius (Linnaeus, 1758), in the Danube River near the confluence with the Sava River (Serbia)

Abstract

A sample of 198 asp (Aspius aspius) was collected over a 28.5 km long section of the Danube River, upstream and downstream from the mouth of the Sava River, in order to provide information on population structure, diet, growth, and condition of this species. Total body lengths of sampled fish were 90-405 mm, and body weights 5-567 g. The sample was predominantly sub-adult fish aged 0+ to 4+ years. Sexually immature asp prevailed over the sexually mature asp. The sex ratio (1.4 : 1) was biased toward males. Male asps in the Danube become sexually mature only in their fifth year of life, and the females even later, as no sexually mature females were caught. The diet spectrum consists exclusively of fishes; of seven determined prey species, most important are bleak Alburnus alburnus, roach Rutilus rutilus, and goldfish Carassius auratus. Highest value of the seasonal vacuity index is in November (I v = 94.1), and the smallest in July (I v = 35.6). Trophic niche breadth is largest in May (H = 1.40), and smallest in November (H = 0.00). The largest average number of prey items is found in age class 4+ (2.33), the smallest in age class 0+ (1.00). Von Bertalanffy growth parameters are L ¥ = 526.46, K = 0.28, and t 0 = 0.22. The length-weight relationship is described as log W = )5.16 + 3.03 log L. FultonÕs condition factor increases with fish length, from 0.70 to 0.83. Regarding seasonal fluctuations, this factor begins to increase in late spring, with the trend continuing until autumn, and then decreasing from autumn to spring.

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“…Our current observation from the middle reaches of Euphrates showed comparable TL at maturity for the asp although female age at first maturity could be younger than those from other sections of the River. European asp reaches sexual maturity at 4+ years with an average total length of 42.5 cm in their native habitats (Teletchea et al, 2009;Krpo-Ćetković, et al, 2010). We also concluded significant correlations between fish length and weight with absolute fecundity for asp in the studied area which were not observed before in northern populations (Oymak, et al, 2011).…”

“…Meanwhile, spawning season of asp from Turkey, the northern section of Euphrates-Tigris Basin, start in April and last until May (Oymak et al, 2011). European asp spawning season occurs within April-May when female can have an average absolute fecundity of 200 thousand eggs (Teletchea et al, 2009;Krpo-Ćetković et al, 2010). Our findings showed that the spawning season occurs within February-March in the study area which signifies the latitude effect in terms of temperature on poikilotherms.…”

“…Sampling sites covered around 200 km to the north and to the south of Deir ez Zor city (35°20′N, 40°9′E) by the Euphrates River (Figure 1). For each obtained specimen, total length (L, to nearest 0.1 cm) and weight (W, to nearest g) were recorded and age estimated by examining the relatively proportionalshape scales as validated for other Asp species (Martyniak and Heese, 1994;Krpo-Ćetković, et al, 2010). Weight-length relationship for males, females and both sexes were computed separately.…”

Patterns in diel habitat use of fish covering the littoral and pelagic zones in a reservoir

“…bleak; avoiding the pelagic and staying close to the safer littoral zone during day, is driven by high occurrence of their predators in the pelagic zone. High numbers of asp larger than 200 mm were detected in the pelagic zone at day and bleak is very important part of asp diet (Krpo-Ć etković et al, 2010). Several studies have suggested that nocturnal predators can influence small fish distribution at night (Brabrand & Faafeng, 1993;Hölker et al, 2007).…”

Stable isotopes and gut contents indicate differential resource use by coexisting asp (Leuciscus aspius) and pikeperch (Sander lucioperca)

“…Scales and otoliths were taken and used for age determination following validated methods described by Ruuhijärvi, Salminen, and Nurmio (1996) and Krpo-Ćetković, Hegediš, and Lenhardt (2010). Scales and otoliths were taken and used for age determination following validated methods described by Ruuhijärvi, Salminen, and Nurmio (1996) and Krpo-Ćetković, Hegediš, and Lenhardt (2010).…”