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European anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) are southern, warm water species that prefer temperatures warmer than those found in boreal waters. After about 40 years of absence, they were again observed in the 1990s in increasing quantities in the North Sea and the Baltic Sea. Whereas global warming probably played a role in these northward migrations, the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO) and the contraction of the subpolar gyre were important influences. Sardine re-invaded the North Sea around 1990, probably mainly as a response to warmer temperatures associated with the strengthening of the NAO in the late 1980s. However, increasing numbers of anchovy eggs, larvae, juveniles and adults have been recorded only since the mid-1990s, when, particularly, summer temperatures started to increase. This is probably a result of the complex dynamics of ocean–atmosphere coupling involving changes in North Atlantic current structures, such as the contraction of the subpolar gyre, and dynamics of AMO. Apparently, climate variability drives anchovies and sardines into the North and Baltic Seas. Here, we elucidate the climatic background of the return of anchovies and sardines to the northern European shelf seas and the changes in the North Sea fish community in the mid-1990s in response to climate variability.

The Workshop on Long‐term Variability in Southwestern Europe (WKLTVSWE) was held in Lisbon, Portugal from 13 to 16 February 2007, a joint effort of ICES and GLOBEC and endorsed by EUR‐OCEANS (http://www.eur‐oceans.org). In 1997, GLOBEC’s SPACC (Small Pelagic Fish and Climate Change) initiative held a joint meeting with SCOR Working Group 98 on worldwide, large‐scale fluctuations in sardine (Sardinops sagax) and anchovy (Engraulis spp.) populations (Schwartzlose et al., 1999). It was decided then to continue this “global” undertaking with a series of regional workshops. Previous meetings had focused on the Benguela Current in 2001 (Cury and Shannon, 2004), the Humboldt Current in 2002 (Alheit and Niquen, 2004), and Japanese waters in 2003. During the 2005 annual meeting of the former ICES Study Group on Regional Ecology of Small Pelagics (SGRESP) – subsequently ICES/GLOBEC Working Group on Life Cycle and Ecology of Small Pelagic Fish (WGLESP) – it was recommended that this series of workshops be continued with a meeting focusing on the waters surrounding the Iberian Peninsula, including the western Mediterranean Sea., 0

Decade-scale regimes of sardine Sardinops sagax and anchovy Engraulis spp. have been observed in the productive coastal waters of the North-Western, North-Eastern and South-Eastern Pacific and the South-Eastern Atlantic. In each of these systems, the two genera fluctuate out of phase with each other. The subdominant genus may initiate a recovery while the other species is still abundant, so population growth is not necessarily a response to a vacant niche. Rather, it appears to be triggered by formation of one or a few powerful year-classes. At high population levels,quality of sardine and their eggs decreased in Japan, leading to decreased production and survival of eggs, poor yearclasses and stock collapse. Excessive fishing of strong year-classes early in the recovery stage may prevent a species from assuming dominance, so influencing the natural succession of species. This may greatly alter the structure andfunctioning of an ecosystem. For example, a mesopelagic forage fish may replace an epipelagic one, with severe repercussions for predators that can only feed in the upper ocean, e.g. some seabirds. Biological factors also may influence the succession of forage fish. For example, off California, peaks in abundance of predatory species such as bonita Sarda, and chub mackerel Scomber, separate those of the planktivorous sardine and anchovy. In the Pacific Ocean, sardine distribution has change greatly. Compared with its range when scarce, a population at a high levelof biomass can extend 1 000–1 800 miles farther along the coast and 400–2 200 miles farther out to sea. In different periods of high biomass, sardine did not always have the same distribution. In the 1930s and 1940s, near simultaneous fluctuations of sardine in the North-Western and North-Eastern Pacific were in phase. In the 1980s and 1990s,sardine in the North-Western and South-Eastern Pacific were fluctuating in phase. However, along the west coast of North America, sardine started their most recent increase later than in other regions of the Pacific Ocean. This increase is continuing, whereas sardine populations in the North-Western and South-Eastern Pacific have decreased both in catch and geographic distribution since the late 1980s. Therefore, the North-Eastern Pacific has moved out of phase with other major Pacific sardine populations. This may be because abundance of sardine in the CaliforniaCurrent has not yet reached a level at which density-dependent effects exert a major influence. Sardine and anchovy in the South-Eastern Atlantic have been out of phase with populations in the Pacific Ocean, especially those off Peru and Chile. Over the last 300 years, episodic fisheries for Bohuslän herring Clupea harengus in Sweden coincide with periodsof high anchovy abundance off California. Near simultaneous fluctuations of fish stocks in widely separated regions support the view that they are sometimes influenced by climate operating at a global scale. Changes of the gyre-scale circulation seem to be major factors in the decadal climate. In Australia, sardine have a wide range, but the less productive waters support a much lower biomass than is found in the other four systems. Engraulis occur in some systems from which Sardinops are absent, for example, Brazil, where they and Sardinella are segregated verticallyin the water column.

Warnsignal Klima: Die Meere - ��nderungen & Risiken

Decade-scale regimes of sardine Sardinops sagax and anchovy Engraulis spp. have been observed in the productive coastal waters of the North-Western, North-Eastern and South-Eastern Pacific and the South-Eastern Atlantic. In each of these systems, the two genera fluctuate out of phase with each other. The subdominant genus may initiate a recovery while the other species is still abundant, so population growth is not necessarily a response to a vacant niche. Rather, it appears to be triggered by formation of one or a few powerful year-classes. At high population levels, quality of sardine and their eggs decreased in Japan, leading to decreased production and survival of eggs, poor year-classes and stock collapse. Excessive fishing of strong year-classes early in the recovery stage may prevent a species from assuming dominance, so influencing the natural succession of species. This may greatly alter the structure and functioning of an ecosystem. For example, a mesopelagic forage fish may replace an epipelagic one, with severe repercussions for predators that can only feed in the upper ocean, e.g. some seabirds. Biological factors also may influence the succession of forage fish. For example, off California, peaks in abundance of predatory species such as bonita Sarda, and chub mackerel Scomber, separate those of the planktivorous sardine and anchovy. In the Pacific Ocean, sardine distribution has change greatly. Compared with its range when scarce, a population at a high level of biomass can extend 1 000-1 800 miles farther along the coast and 400-2 200 miles farther out to sea. In different periods of high biomass, sardine did not always have the same distribution. In the 1930s and 1940s, near simultaneous fluctuations of sardine in the North-Western and North-Eastern Pacific were in phase. In the 1980s and 1990s, sardine in the North-Western and South-Eastern Pacific were fluctuating in phase. However, along the west coast of North America, sardine started their most recent increase later than in other regions of the Pacific Ocean. This increase is continuing, whereas sardine populations in the North-Western and South-Eastern Pacific have decreased both in catch and geographic distribution since the late 1980s. Therefore, the North-Eastern Pacific has moved out of phase with other major Pacific sardine populations. This may be because abundance of sardine in the California Current has not yet reached a level at which density-dependent effects exert a major influence. Sardine and anchovy in the South-Eastern Atlantic have been out of phase with populations in the Pacific Ocean, especially those off Peru and Chile. Over the last 300 years, episodic fisheries for Bohuslän herring Clupea harengus in Sweden coincide with periods of high anchovy abundance off California. Near simultaneous fluctuations of fish stocks in widely separated regions support the view that they are sometimes influenced by climate operating at a global scale. Changes of the gyre-scale circulation seem to be major factors in the decadal climate. In Australia, sardine have a wide range, but the less productive waters support a much lower biomass than is found in the other four systems. Engraulis occur in some systems from which Sardinops are absent, for example, Brazil, where they and Sardinella are segregated vertically in the water column.

1 TOCA Summary 00 2 TOCA Introduction 00 3 TOCA Decadal-scale regime shifts 00 4 TOCA California Current ecosystem (CCE) 00 5 TOCB Changes in the biota 00 6 TOCB Regime shifts 00 7 TOCB Mechanisms linking climate to decadal-scale 8 population dynamics 00 9 TOCA Kuroshio Current ecosystem (KCE) 00 10 TOCB Changes in the biota 00 11 TOCB Regime shifts 00 12 TOCB Mechanisms linking climate to decadal-scale 13 population dynamics 00 14 TOCA Humboldt Current ecosystem (HCE) 00 15 TOCB Changes in the biota 00 16 TOCB Regime shifts 00 17 TOCB Mechanisms linking climate to decadal-scale 18 population dynamics 00 19 TOCA Benguela Current ecosystem (BCE) 00