Climate Warming and Pikeperch Year-Class Catches in the Baltic Sea

Abstract

Climate change scenarios concerning the Baltic Sea predict increase in surface water temperatures. Pikeperch (Sander lucioperca (L.)) inhabits the coastal areas of the northern Baltic Sea and is an important fish species for the Finnish fisheries. The year-class strength of pikeperch varies strongly between years and significantly depends on water temperature. We aimed to study the effects of changing temperature conditions on pikeperch fisheries and distribution based on commercial catch data from the period 1980-2008 in the Finnish coastal areas of the Baltic Sea. The results indicated that warmer summers will produce stronger pikeperch year-classes that consequently contribute significantly to the future catches. The average temperature in June-July explained 40% of the variation in the year-class catches in the Gulf of Finland and 73% in July-August in the Archipelago Sea. During the study period, the distribution of pikeperch catches expanded toward north along the coasts of the Bothnian Sea.

Pikeperch (Sander lucioperca (L.)) in Decline: High Mortality of Three Populations in the Northern Baltic Sea

“…In line with previous studies (Kjellman et al 2003;Lappalainen et al 2003;Pekcan-Hekim et al 2011), we found a positive relationship between pikeperch YCS and temperature. This result, as well as the strong and weak year classes corresponded to previous studies (Finnish Game and Fisheries Research Institute 2006;Pekcan-Hekim et al 2011).…”

“…This result, as well as the strong and weak year classes corresponded to previous studies (Finnish Game and Fisheries Research Institute 2006;Pekcan-Hekim et al 2011). Also the increases and decreases in the commercial pikeperch fishing catches were rather similar to those recorded from the Finnish Archipelago Sea (Lappalainen et al 2002;Heikinheimo et al 2006;PekcanHekim et al 2011).…”

“…Opposite to earlier studies by Heikinheimo et al (2006) and Pekcan-Hekim et al (2011), we observed nearly as high mortalities at the age of 3-4 years as in older ages, which together with the length distribution in the mesh size of 45 mm suggests that pikeperch may already be caught as by-catch at the age of 4 years. In Galtfjärden, also predation by great cormorant may affect mortalities at ages 3 and 4 years.…”

“…There is a lot of evidence on that larger and thus older females in many fish species have better spawning success than the younger ones (Berkeley et al 2004;Olin et al 2012). Because the year classes of pikeperch are stronger in warm summers (Kjellman et al 2003;Pekcan-Hekim et al 2011) and pikeperch prefer turbid water (Veneranta et al 2011), they are generally expected to benefit from eutrophication and rising sea temperatures (Lehtonen et al 1996;PekcanHekim et al 2011;Veneranta et al 2011).…”

“…In the Finnish Archipelago Sea the catches of pikeperch increased during the 1990s, but declined again during the 2000s (Lappalainen et al 2002;Finnish Game and Fisheries Research Institute 2006;Pekcan-Hekim et al 2011). The increase in catches in the 1990s was in part due to strong year classes of 1988and 1991(Pekcan-Hekim et al 2011), but also due to increased fishing pressure since the late 1990s, which was caused by the decrease of cod (Gadus morhua (L.)) in the 1980s. These factors in combination with restrictions on salmon (Salmo salar (L.)) fishing and an increase in pikeperch price caused an increase in catches, which was probably larger than the actual increase in the stock size (Lappalainen et al 2002).…”