Wild fish and other aquatic organisms as feed in aquaculture in Europe 237
availability or climatic conditions. There are also the genetic effects associated with
removing large amounts of the gene pool, which may adversely affect populations over
long time periods. Indirect effects may also include ghost fishing resulting from lost
fishing gears, which may continue to catch and disturb biological communities and
habitats unmonitored (Chopin et al., 1996; Laist, 1996).
Bycatch
The incidental catch of non-target species, and in particular the capture of juveniles of
commercial species, is one of the most controversial aspects of feed fisheries, as most
undersized fish are landed and processed. In North Atlantic waters, juvenile herring
are known to shoal with sprat (Hopkins, 1986), while juveniles of other commercial
species such as whiting and haddock are known to shoal with industrial teleost
feedfish such as Norway pout (Huse et al., 2003; Eliasen, 2003). Bycatch levels are not
necessarily high – the bycatch in the Danish and Norwegian North Sea sand-eel fishery
(mainly herring, saithe and whiting) has averaged 3.5 percent over 1997–2001 (ICES,
2003a). While levels are low, given the scale of the feed fisheries being prosecuted,
actual quantities of bycatch can be significant. In 2002, the Danish sand eel landings
accounted for 622 100 tonnes, of which 3.7 percent was considered bycatch, totalling
23 018 tonnes of herring, cod, haddock, whiting, saithe and mackerel. In the same
period, the sprat fishery took 27 972 tonnes of bycatch. In 2003, an experimental trawl
survey (CEFAS, 2004) used a 16 mm commercial sand-eel net to monitor the whitefish
bycatch on the West Dogger sand-eel grounds. Sand eels comprised 50–65 percent
of the catch, below that required to meet EU catch composition rules, but sand-eel
abundance was exceptionally low in 2003. Adult cod and haddock were not caught in
the sand-eel net, which was capable of retaining 0-group gadoids (whiting), but their
distribution was patchy, and no juvenile cod were caught.
There is recent evidence of declining bycatch in the sand-eel fisheries and the blue
whiting fishery as seen in the Danish feed-fish catches (Table 19). Bycatch is an issue
in the sprat fisheries, where increased herring bycatch is largely a result of relative
increases in abundance (ICES, 2003b).
The composition and volume of catches from the Norwegian industrial fisheries,
which target both blue whiting and Norway pout, was reported by ICES (2003b).
Between 2000 and 2002, the average annual landings from the mixed fishery was
109 000 tonnes. Blue whiting formed an estimated 58 percent of this catch, while
Norway pout formed approximately 17 percent. The remaining 25 percent, or about
16 000 tonnes, consisted of a range of fish and invertebrates. The six most important
bycatch species (in terms of landed catch) were saithe, herring, haddock, Atlantic horse
mackerel, whiting and mackerel, each of which represented an annual catch of at least
1 000 tonnes in this fishery. This length distribution analysis suggests that the bycatch
of these species consisted primarily of immature individuals.
In the North Sea, this issue has been addressed by closures of part of the North Sea
to Norway pout fishing to reduce the bycatch of juvenile commercial species. Similarly,
seasonal closures exist for the conservation of fishery resources through technical
measures for the protection of juveniles of herring and sprat (EC Regulation 850/98;
Council of the European Union, 1998). Bycatch regulations and minimum mesh size
are also in place, aimed at reducing juvenile bycatch.
The spatial and temporal distribution of cod bycatch in the herring and sprat
fisheries of the Baltic Sea was thought to relate to the co-occurrence of the three species
on cod and sprat pre-spawning and spawning grounds. ICES (2001) determined that
the share of bycatch in total landings of cod was within the range of 1.3 to 2.0 percent.
The bycatch in pelagic fisheries, therefore, appeared to have a minor effect on the cod
population.