Total marine fisheries extractions by country in the Baltic Sea

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14 Total marine fisheries extractions by country in the Baltic Sea: 1950-present, Rossing, Booth and Zeller Table 5. Default anchor points (%) used for estimating unreported landings of other taxa, excluding cod and salmon in the Baltic Sea based on sources (Tables 2.3.1 and 2.4.1 in ICES, 2007; and Table 2.1.2 in ICES, 2008b). Dash (-) indicates year of linear interpolation between anchor points. Countries Year Western Eastern 1950 5.0 a 0.0 d 1951-1979 - 0.0 d 1980 10.1 b 0.0 d 1981-1990 - 0.0 d 1991-1992 - - 1993 20.3 20.3 1994 26.9 26.9 1995-2003 - - 2004 12.3 12.3 2005 11.2 11.2 2006-2007 11.2 c 11.2 c a b assumption of 5% of reported landings; assumption of ½ the reported rate for 1993; c 2005 value; d assumption of zero unreported catches. interpolations were done between anchor point years. For eastern bloc countries, unreported landings were assumed to be zero until 1990 after which unreported landings were estimated using linear interpolations between anchor points. Discards Underwater discards: Estimates of underwater discards were applied for all countries in all years, but to herring and sprat catches only. While other gear types targeting other species are likely to also experience underwater discarding, we had no information to reliably apply this to other gear types. Hence, our estimates of this type of discarding are conservative. Sprat and herring, which are targeted by the same trawl fleet, may be caught simultaneously in trawl gear no matter which species is the primary target. Inaccurate catch composition data for these two species, and the fact that they are both targeted by the same fleet, led us to apply the underwater discard rate to both species combined (M. Rahikainen, pers. comm., University of Helsinki). A Finnish study examined mortality levels associated with underwater discards in the herring trawl fishery (Rahikainen et al., 2004). This study used length-age relationships to determine the number of fish by age class that were lost from trawl gear while it was deployed fishing, and also to determine the amount of catch brought on board. We converted the numbers-at-age to weights using average weights from ICES (2008a) for age classes 1 – 12 and information from Cardinale (2000) for age zero herring to determine the weight of fish that were lost prior to gear retrieval. We then determined the rate of underwater discards by deriving a ratio of underwater discards to the amount of fish brought on board. We quantified the loss as approximately 9% of catches brought on board. We also applied this underwater discard rate to sprat since it is likely that underwater discards are similar to those of herring (M. Rahikainen, pers. comm., University of Helsinki). Trawl landings of herring and sprat by Denmark and Finland had 9% added to their landings (ICES landings + adjustments + unreported landings) to account for underwater discards. All Discards were separated into four categories: 1) ‗underwater‘ discards caused by deployed gear engaged in fishing; 2) ‗ghostfishing‘ caused by gear that is lost, but continues to fish; 3) ‗boat-based‘ discards resulting from fisher‘s behavior after the catch is brought on board; and 4) ‗seal-damaged‘ discards. Available information on discards was converted into a percentage rate to apply to the sum of ICES landings, adjustments and unreported landings. ICES stock assessment working group reports contain data on discards for the eastern and western cod stocks (ICES, 2007; 2008a), and for salmon (ICES, 2008b). Separate studies provided data on underwater discards by active fishing gear (Rahikainen et al., 2004) and ghostfishing by lost gear (Tschernij and Larsson, 2003; Brown et al., 2005). A Danish study (Anon., 2006) examined boat-based discard practices for their entire fleet over a one year period and these data were used to derive default discard rates for species other than cod and salmon. Table 6. Anchor points (%) used for estimating boat-based discards of eastern cod by western countries in the Baltic Sea (Sources: Tables 2.4.1 and 2.4.5b in ICES, 2007; Table 2.4.1, 2.4.5b and 2.4.20 in ICES, 2008a). Former eastern bloc countries had the same rates applied beginning in 1993. Year Anchor Anchor Year point point 1950-1965 10.0 a 1987 5.9 1966 9.2 1988 4.5 1967 12.4 1989 1.9 1968 8.3 1990 3.0 1969 9.6 1991 2.2 1970 6.6 1992 3.5 1971 4.7 1993 3.4 1972 12.7 1994 2.1 1973 8.9 1995 1.7 1974 10.5 1996 1.2 1975 10.4 1997 3.9 1976 2.3 1998 3.4 1977 1.6 1999 2.5 1978 15.5 2000 6.8 1979 16.0 2001 3.2 1980 3.6 2002 2.2 1981 16.3 2003 2.8 1982 5.8 2004 1.8 1983 4.7 2005 3.0 1984 2.3 2006 13.2 1985 3.1 2007 11.3 1986 1.2 - - a assumption based average from 1966-1968.
Total marine fisheries extractions by country in the Baltic Sea: 1950-present, Rossing, Booth and Zeller 15 Table 7. Anchor points (%) used for estimating boat-based discards for western cod by western countries in the Baltic Sea based on sources (Table 2.3.6 in ICES, 2007; Tables 2.3.1 and 2.3.6, and Figure 2.3.1 in ICES, 2008a). Former eastern bloc countries had the same rates applied beginning in 1993. Year Anchor point Year Anchor point 1950-1969 65.1 a 1989 77.9 1970 71.5 1990 79.4 1971 57.0 1991 96.0 1972 66.9 1992 19.2 1973 21.3 1993 14.5 1974 42.6 1994 10.6 1975 22.4 1995 11.3 1976 18.3 1996 15.7 1977 25.6 1997 10.0 1978 27.5 1998 17.3 1979 10.8 1999 11.6 1980 17.1 2000 12.5 1981 13.8 2001 11.2 1982 35.3 2002 10.4 1983 40.7 2003 15.8 1984 17.9 2004 10.1 1985 71.8 2005 18.6 1986 15.2 2006 8.6 1987 20.8 2007 8.3 1988 10.2 - - a assumption based average from 1970-1973. other countries had a more conservative rate of 5% added to their estimated landings of herring and sprat (i.e., ICES landings + adjustments + unreported landings) since landings by gear type were not available. Ghostfishing: Ghostfishing is a global problem (Macfadyen et al., 2009) that results from fishing gear that continues to fish after it is lost at sea for various reasons (Brown et al., 2005). Since fishing gear is now mostly made of synthetic material, it can continue to fish, and it has been found that a lost cod gillnet can continue to catch fish for as long as two years after being lost (Tschernij and Larsson, 2003). A ghostfishing rate of 1.65% was applied to all species excluding pelagic species (e.g., herring and sprat) for all countries in all years based on data presented in Brown et al. (2005). Boat-based discards and seal-damaged discards: Boatbased discarding was treated separately for the former eastern bloc countries and the western countries from 1950 to 1990. Thereafter, former eastern bloc countries‘ data were linearly interpolated from the assumed value of zero for the 1950-1990 time period to values reported in 1993. After 1993, when the eastern bloc countries became market oriented economies, the rules from the western countries were applied to the former eastern bloc. Data used for default boat-based discard estimates for the eastern cod stock (Table 6), the western cod stock (Table 7), and for salmon (Table 8) were based on ICES stock assessment working group reports (ICES, 2007; 2008a; 2008b), and discards for all other taxa were based on a study that documented discards for all Danish fleets over a one-year period (Anon., 2006). To assess discards backwards in time, an assumption-based approach was used. For the former eastern bloc countries, prior to becoming market-oriented economies, it was assumed that all species, excluding herring and sprat, were discarded at a rate of 2% per year from 1950-1990. After 1990, the discard rates were interpolated to the anchor points in 1993 for salmon, cod and all other taxa (Anon. 2006). For western countries, ICES stock assessment working group reports have estimates of discards beginning in 1966 for the eastern cod stock, 1970 for the western cod stock, and 1981 for salmon. These discard estimates were reported as a single number for all countries in each year, and given the assumed 2% discard rates for the former eastern bloc countries, an adjustment could be made for the 1950 to 1990 time period to the reported discard amounts based on the discard rates for the former eastern bloc countries in each year of reported discards, Western countries‘ discard rate = [reported discards – (0.02*eastern bloc landings)]/western countries‘ landings Discards by western countries of the eastern cod stock were reported from 1966-2007 in ICES working group reports (ICES, 2007; 2008a). For the period 1950 to 1965, the average rate of discards from the first three years of reported data (i.e., 1966-1968) were applied to estimate discards. Discards by the western countries of the western cod stock are reported from 1970 to 2007 (ICES, 2007; 2008a). The average discards reported for the first three years of reported data (i.e., 1970-1972) in the ICES stock assessment working group reports were transformed into an average rate and applied to the 1950-1969 time period. In order to assess salmon discards, two basic data sources were available. Data originating from the ICES stock assessment working group report (ICES, 2008b) detailing Baltic-wide estimates of boat-based discards of salmon, which are known to include discards due to seal damage, that cover the time period 1981 to 2007 (Table 8), and data obtained from the Finnish Game and Fisheries Research Institute (FGFRI) detailing the level of discards resulting from seal damage only in Finland that covered the time period 2000 to 2007 (A. Ahvohenen and P. Söderkultalahti, pers. comm., FGFRI). In years of data overlap
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Total marine fisheries extractions by country in the Baltic Sea

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