Abstract

The distribution of fish and prawn in the bed of the lower Amur River (within 40–960 km from the mouth) is described based on the results of a beam-trawl survey (57 trawl taw at depths of 1.5–23.0 m) conducted in September and October 2003. A total of 2584 ind. of 22 fish species and 1077 ind. of one invertebrate species (the prawn Palaemon modestus) were caught. The most frequently occurring fish species were members of the orders Cypriniformes (13 species) and Siluriformes (4 species). The total number of benthic and demersal fish was estimated at 32.161 million ind.; the total number of prawn was estimated at 4.887 million ind. The most abundant fish were two commercial catfish species: the Brazhnikov’s catfish Tachysurus brashnikowi (estimated at 16.26 million fish) and the Chinese catfish T. sinensis (4.32 million fish). The abundance of both fish and prawn increased by many times towards the mouth of the Amur, which correlated with the increasing biomass of the benthic food supply in the same direction. The total biomass of fish and prawn equaled 583.8 and 8.8 t, respectively. The fish biomass varied in the 0.012–2.572 g/m² range (with an average of 0.450 ± 0.270 g/m²) and the prawn biomass varied within 0.005–0.044 g/m² (0.021 ± 0.012 g/m²). The major portion of the fish biomass (82.4%) was recorded mainly from the lower reaches of the Amur River (40–400 km from the river mouth); the entire prawn biomass was concentrated in the lower reaches (50–150 km from the mouth). The following fish species were dominant in catches in terms of biomass: Chinese catfish (32.9%), Brazhnikov’s catfish (24.0%), Chinese lizard gudgeon Saurogobio dabryi (12.6%), Ussuri catfish T. ussuriensis (9.7%), Amur whitefin gudgeon Romanogobio tenuicorpus (7.8%), Amur sturgeon Acipenser schrenckii (5.6%), Siberian gudgeon Gobio cynocephalus (2.4%), and kaluga Huso dauricus (0.6%).