Contrasting responses in larval and juvenile growth to a climate–ocean regime shift between anchovy and sardine

Abstract

Anchovy and sardine populations have fluctuated alternately with decadal changes in climatic and oceanic states, although the mechanisms remain unclear. In the western North Pacific, anchovy and sardine share nursery grounds in the Kuroshio–Oyashio transitional waters, where the subtropical and subarctic currents converge from the south and north, respectively. We found that northward expansion of the subtropical waters simultaneously changed the local environment in the nursery grounds to be favorable for late larvae and early juveniles of anchovy, but not for those of sardine during 1996–2002. Increased temperature enhanced growth and survival for anchovy, whereas reduced food availability diminished those for sardine. Northward expansion of the subtropical waters have been linked with wind-forced anomaly of sea-surface height in the central North Pacific. After 1988, when anchovy flourished and sardine collapsed in the western North Pacific, previous studies by other researchers documented similar changes in air–sea interaction. Our results suggest that contrasting responses in growth and survival processes to wind-forced oscillation of the current structures caused the alternate population dynamics between anchovy and sardine in the western North Pacific.

Winter mixed layer depth and spring bloom along the Kuroshio front: implications for the Japanese sardine stock

“…Nishikawa & Yasuda (2008) reported significant negative correlations between mortality and the winter mixed layer depth (MLD) in regions of the KE and suggested the importance of spring feeding conditions, which may be controlled by the wintertime entrainment of subsurface nutrients. Takahashi et al (2008Takahashi et al ( , 2009 re ported that interannual variations in the growth rates of early stage juveniles corresponded to recruitment variability in the low-stock period of 1996 to 2003.…”

Simulation of copepod biomass by a prey–predator model in Hiuchi-nada, central part of the Seto Inland Sea: does copepod biomass affect the recruitment to the shirasu (Japanese larval anchovy Engraulis japonicus) fishery?

“…Japanese anchovy flourish in the western North Pacific when the sea surface is warmer, while the sardine flourishes when the sea surface is cooler [12]; therefore, sea temperature was the first factor studied to determine the recruitment of anchovy or sardine [13][14][15]. However, many fishery scientists have argued that it is essential to understand the functional role of the copepod assemblage as a food resource in determining the recruitment abundance of pelagic fish populations (e.g., anchovies, sardines, and herrings) [14][15][16][17][18][19]. Copepods are the most dominant mesozooplankton group in the world's seas and are the main food item for most marine fish larvae in the form of eggs, nauplii, and copepodids [20][21][22].…”

Catch Predictions for Pacific Anchovy Engraulis japonicus Larvae in the Yellow Sea

“…Oceanographic conditions affect survival rates in all life stages, but this is particularly true in early life stages (Cushing, 1975;Lasker, 1981;Rutherford and Houde, 1995;Takahashi et al, 2009;Takasuka et al, 2003Takasuka et al, , 2004. Annual variation in recruitment conditions and the subsequent survival of anchovy larvae in the Yellow Sea can be influenced by variability in oceanic conditions.…”

“…Large fluctuations in recruitment may be influenced by subtle variation in mortality rates, growth rates, or the dura- west coast"), based on the Annual statistics on cooperative sales of fishery products (National Federation of Fisheries Cooperatives, 1998-2009 Relationships between larval catch data and egg density and oceanographic parameters were estimated using Pearson's correlation coefficients and linear regression using PROC REG in SAS version 9.1 (SAS, 2004). Anchovy mainly spawn in June-July and grow to larvae and juveniles in July-October.…”