Total marine fisheries extractions by country in the Baltic Sea

Total marine fisheries extractions by country in the Baltic Sea: 1950-present, Rossing, Booth and Zeller 243
made to minimize or avoid it. The effects of discarding on the ecosystem are to a large extent unknown and
in order to improve the understanding and also stock assessments it is necessary that all discards are
reported (Anon., 2003a). Generally, the only way in which actual catches (i.e., reported and unreported
landings and discards) can be properly accounted for, is through 100% observer coverage on all vessels of
all fleets. Anything less than 100% coverage results in often strong observer bias effects leading to
unreliability and high uncertainty in the observer data (Babcock and Pikitch, 2003; Anon., 2006a;
Bremner et al., 2009).
The estimated recreational catch was about 0.6 million t from 1950-2007, which was 7% of the estimated
total reconstructed catches. Recreational fishing in Sweden is one of the biggest recreational activities and
for some species the recreational catch is several times larger than the commercial landings (Anon.,
2007a). If one excludes the three major commercial species, cod, herring, and sprat (which account for
94% of reported ICES landings statistics), the recreational catches made up nearly 50% of the remaining
total reconstructed catches, none of which is appropriately represented by ICES data. Similar recreational
contributions to total catches have been reported in the USA (e.g., Coleman et al., 2004). Even though the
recreational part of catches is often substantial, the data on recreational fishing in Sweden are very poor,
especially prior to 2006. Hence, better data are needed for recreational fisheries, including species- and
area-specific catch and effort data. These could possibly be obtained through well designed, country-wide
surveys, conducted at least every 3-5 years, with all data for intervening years being interpolated.
Emphasis should also be placed on incorporating these data (surveyed and interpolated) in all annual
reports to ICES.
Much of the available information was biased towards the commercially important species, such as cod,
herring and sprat. Further, the total reconstructed catches were also largely driven by the three major
commercial species that accounted for 94% of the reported ICES landings statistics. These three are also
the ecologically dominating species of fish in the Baltic Sea (Hansson and Nissling,
www.ecology.su.se/projects/images/WWF1.pdf); hence, fishing is a key factor structuring the Baltic Sea
marine ecosystem (Harvey et al., 2003). Consequently, if fishing causes a decline, or even collapse of a fish
population in the Baltic Sea, it does not only affect the fisheries (and stock), but it likely also has
substantial ecosystem implications (Harvey et al. 2003). For example, multi-level trophic cascade effects
have recently been reported for the Baltic Sea, driven mainly by overfishing of cod that enabled substantial
increases of sprat during the 1990s due to predation release (Casini et al., 2008). This increase in sprat
populations in turn led to a decline of zooplankton, the food of sprat, which in turn reduced grazing
pressure on phytoplankton, contributing to algal blooms. The potentially harmful algal blooms were
previous exclusively ascribed to eutrophication and climate conditions (Casini et al., 2008). Low densities
of zooplankton also harm the recruitment of pike and perch (Ljunggren et al., 2008), and problems with
recruitment for these two species exist along the Swedish coast of the Central Baltic Sea (Ask and
Westerberg, 2008).
Sweden has an extensive tradition of scientific research. Many of the laboratories and research stations
that form the national marine research foundation were founded in the 1930s
(www.fiskeriverket.se/vanstermeny/omfiskeriverket.4.1e93312510e313daf128000225.html). Yet, there is
a lack of data and understanding about fisheries impacts on the Baltic Sea ecosystems beyond the single
species stock assessments and the most basic, direct effects of fishing. More ecosystem-level research is
needed, and larger safety margins in Total Allowable Catch (TAC) should be applied (Hjerne, 2003). One
key requirement is for better accounting of total catches, not only commercial landings data. As suggested,
compulsory 100% observer coverage (onboard observer and/or remote video monitored) on all
commercial fishing vessels would improve accounting of total catches (Anon., 2005d).
Unreported landings
The estimated unreported landings are thought to be conservative and therefore minimum estimates. Out
of a total 1.09 million t unreported landings, more than 66% came from unreported landings during the
1980s and the 1990s. This reflects the limited information available for the present study, but is also a
result of the cautious assumptions and conservative methods chosen here for this catch reconstruction.
Based on the assumption that the introduction of quotas increased the incentive for un- and
underreporting (Søndergaard, 2007), a break point was set to 1980. Further, several sources indicated that
unreported landings have declined in recent years (K.-E. Karlsson, pers. comm., Swedish Tax Agency; B.
Sjöstrand, J. Löwenadler Davidsson, pers. comm., Swedish Board of Fisheries), hence, the effort to remain
conservative when setting anchor points in the 2000s.