Changes in the lower trophic levels as a consequence of the level of fish manipulation in the ponds

✍ Scribed by István Tátrai; János Oláh; Gábor Paulovits; Kálmán Mátyás; Barbara J. Kawiecka; Ferenc Pekár

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 548 KB
• Volume: 82
• Category: Article
• ISSN: 1434-2944
• DOI: 10.1002/iroh.19970820208

✦ Synopsis

Abstract

Cyprinid fish of different mature age classes (3+ ‐4+) and stocks (100, 300 and 500 kg/ha) were introduced into each of three experimental ponds with area of 0.3 ha (average depth ca 1.7 m) while the fourth pond was left free of fish. Bream (Abramis brama L.), white bream (Blicca bjoerkna L.) and roach (Rutilus rutilus L.) made up 75% of the total cyprinid biomass, with wild carp (Cyprinus carpio L.) as the remaining 25%. The introduced fish spawned successfully.

The high (above 300 kg/ha) planktivorous and benthivorous fish stocks resulted in several qualitative and quantitative alterations of the food chain structure in our simulation pond experiments. These alterations must primarily be assigned to changes caused by both the zooplanktivory and benthivory nature of the stocked fish populations. At the higher levels of fish biomass, Secchi depth was influenced significantly by chlorophyll‐a concentration. Most of the variance in suspended solids concentration could be explained by the biomass ratio of the mature benthivorous fish. There was a clear shift in algal cell size in the ponds with the higher fish stocks: ponds with more fish had larger cells later in the summer. The relative influence of young cyprinid fish on crustaceans species composition and biomass, and mature populations on benthic fauna abundance and biomass, was sufficiently greater at higher (300–500 kg/ha) fish stock rates.