Total marine fisheries extractions by country in the Baltic Sea

24 Total marine fisheries extractions by country in the Baltic Sea: 1950-present, Rossing, Booth and Zeller
Various sources have speculated unreported landings to be the greatest component of IUU catches in the
Baltic Sea (Anon., 2007b) and similarly, 46% of our estimated IUU catches were unreported landings. At a
Baltic Sea Regional Advisory Council (BSRAC) meeting, members concluded that unreported landings of
cod represented the greatest aspects of non-compliance in the Baltic Sea (BSRAC, 2007). Unreported
landings of all species contribute to an excess of unaccounted fishing mortalities which skew scientific
data, directly impact decisions made by policy-makers, and mis-lead the public‘s opinion on the health of a
common resource. It also has the potential to substantially bias and even undermine stock assessment and
the resulting scientific advice to management. While ICES stock assessment working groups do try to
account for some unreported landings (‗unallocated catches‘), the lack of country specific data
transparency in ICES stock assessment working group reports make it impossible for interested parties
and the resource owners (general public) to assess country compliance and enforcements (Pfeiffer and
Nowak, 2006).
Our estimates of discards were slightly less significant than unreported landings, comprising
approximately 30% of our overall IUU estimate. We examined several different forms of discarding in our
catch reconstruction including: i) ghostfishing; ii) underwater discards; iii) seal-induced discards; and iv)
boat-based discards. Ghostfishing was recognized in a recently published paper by the FAO (Macfadyen et
al., 2009), to have become an issue of global significance, as abandoned fishing gear now represent an
estimated 10% of all marine litter. Abandoned gear is found to cause mortality in fishes, seabirds and
marine mammals (Macfadyen et al., 2009). For the period from 1950 to 2007, we found ghostfishing to
affect cod most significantly. Overall, ghostfishing was responsible for approximately 330,000 tonnes of
discards over the entire study period. Details of the various discard types are described in each country
specific report (this volume).
We considered underwater discards to be a significant threat to species caught by pelagic trawl fisheries
(herring and sprat). There is no simple solution to mortalities caused by actively fishing gear, except
improved design and modification of gears as a preventative measure (Matsuoka, 2008). Regardless, our
study illustrates the potential magnitude of this mortality, and it is important that these estimates be
included in management decisions for the Baltic Sea LME, including TACs for species directly affected by
trawl gear.
Seal-induced discards were found to be of importance mostly in eastern Baltic countries, and were
considered to affect fisheries catches of herring, salmon, trout, whitefish, perch, pikeperch and vendace
mainly in Estonia, Finland, Latvia, Lithuania and Russia. This problem has been inevitable with current
trap-netting techniques since the early 1990s when grey seal populations increased dramatically. Since
this time there have been several advances in trap-net design which have been successful in reducing
mortalities caused by seal populations. The pontoon trap, described by Hemmingsson et al. (2008) has
demonstrated the best avoidance of seal-induced damages of catches thus far. Mitigation of seal-induced
discards is necessary from biological, economical and social perspectives, as commercial fishers in the Gulf
of Bothnia have suffered significant economic losses in the last two decades (Siira, 2007). Reducing the
damages caused by seals to fish caught in trap-nets in the eastern Baltic is necessary as improved trap-net
design will reduce the overall fishing pressure on salmon stocks. It will also allow fishers to have the
opportunity to be accountable for all catches taken by fishing gear, since estimates of catches taken
completely by seals would become unnecessary.
Boat-based discards were found to be the most significant form of discarding in the Baltic Sea, but in
theory, should be one of the easiest to address, since human behavior is the single determinant. Our catch
reconstruction indicated that boat-based discards of cod were predominant, peaking at approximately
39,500 t∙year -1 in 1972, and accounting for approximately 11,650 t∙year -1 in recent years (2005-2007).
These results are likely due to the effects of high-grading. In addition, large catches of herring have been
known to contain a large amount of cod as bycatch (Alm, 1961). Significant also were the number of boatbased
flatfish discards in proportion to the total reconstructed catch of flatfishes. Given the increasing
concern for, and consideration of ecosystem-based management approaches, such waste is rapidly
becoming a serious management concern and needs to be urgently addressed. Boat-based discards of cod
were rarely higher than about 15% of total catch; discards of flatfishes were consistently greater than 30%
of total catch for flatfishes (as sourced from Jensen, 2004), indicating a potential cause for concern with
regards to the overall fishing pressure exerted on flatfish populations. Flatfish are characteristic lower
value bycatch of the trawl fisheries targeting cod (Alm, 1961), leaving significant potential for high grading
by fishers under current TACs. Reductions in flatfish discards have been made elsewhere by reducing the