J. Jurvelius et al., STOCK ASSESSMENT OF PELAGIC 3-SPINED STICKLEBACK (GASTEROSTEUS-ACULEATUS) - A SIMULTANEOUS UP-LOOKING AND DOWN-LOOKING ECHO-SOUNDING STUDY, Fisheries research, 27(4), 1996, pp. 227-241
Hydroacoustics is a suitable method for estimating the stock size and
spatial distribution of pelagic fish species with low fishing mortalit
y. Pelagic three-spined stickleback (Gasterosteus aculeatus) is such a
species. Its spatial distribution and abundance were studied by hydro
acoustics and trawling in the Gulf of Bothnia in August 1991, Upward a
nd downward looking transducers were used in this round-the-clock surv
ey. Sticklebacks were in the surface layers at night, and during the d
ay they migrated down to 10-20 m depth. The thermocline was at a depth
of 13 m. Sticklebacks had a very patchy horizontal distribution, with
the highest biomass densities being found just north of the Quark are
a (up to 14-28 t NM(-2)) and the lowest in the southern parts of the B
othnian Sea. The areal density of sticklebacks was lowest in the south
ern Bothnian Sea (124 x 10(3) specimens NM(-2)) and highest in the Bot
hnian Bay (3000 x 10(3) specimens NM(-2)). The estimated total biomass
of three-spined stickleback was about 25 000 tons in the pelagic area
s of the Gulf of Bothnia.