H. Peltonen et al., Estimation of roach (Rutilus rutilus (L.)) and smelt (Osmerus eperlanus (L.)) stocks with virtual population analysis, hydroacoustics and gillnet CPUE, FISH RES, 44(1), 1999, pp. 25-36
Dynamics of roach (Rutilus rutilus (L.)) and smelt (Osmerus eperlanus (L.))
stocks were analysed with virtual population analysis (VPA), hydroacoustic
s and by analysing gillnet catches per unit effort (CPUE). The research are
a was the Enonselka: basin of Lake Vesijarvi in southern Finland. In 1989 i
ntensive trawl fishing on previously unexploited roach and smelt stocks was
started. Heavy exploitation continued until 1993. Drastic reductions in fi
sh stock densities were observed. The VPA indicated a decline in the roach
stock from c. 3900 ind. ha(-1) in 1989 to c. 520 ind. ha(-1) in 1993. In th
e smelt stock the VPA indicated a respective decline from c. 18000 to c. 19
00 ind. ha(-1). In 1994-1996 fishing was sustained on a lower level. Anyhow
, hardly any increase in stock density of roach and smelt was observed in 1
994-1996, The estimates with hydroacoustics were in concordance with the VP
A estimates in both the roach and the smelt stock. The gillnet CPUE-estimat
es were in agreement with hydroacoustics in roach stock assessment. However
, gillnet CPUE was not suitable for analysing the dynamics of the smelt sto
ck. (C) 1999 Elsevier Science B.V. All rights reserved.