Regimes and stock-recruitment relationships in Japanese sardine (Sardinops melanostictus), 1951-1995

Abstract

We used reproductive success, rather than abundance or catch, to identify regimes because reproductive success responds faster to environmental changes. Peak abundance of Japanese sardine during 1951-1995 was about 1000 times higher than minimum abundance. A regime shift occurred in the early 1970s when carrying capacity (measured using spawner-recruit models) increased by about 75 times. We hypothesize that this was due to large-scale changes in the Kuroshio and Oyashio Current systems. Long-term environmental variation (regimes), interannual variability in recruitment success, and density-dependent recruitment and growth rates affected dynamics of Japanese sardine. We hypothesize that density-dependent effects on recruitment of Sardinops spp. are common but usually obscured in short data sets by environmental variability and measurement error. Virtual population analysis and forward-simulation modeling approaches gave similar biomass and recruitment estimates. The relationship between sardine biomass and catch per unit search time was nonlinear. Mass-at-age and biomass were correlated, and it may be possible to use mass-at-age as an abundance index. Current abundance is low, and we believe that the environment has shifted to a regime that is unfavorable for Japanese sardine.

Effects of environmental variability on recruitment and bioeconomic modelling in the Pacific sardine (<em>Sardinops sagax caerulea</em>) fishery from Magdalena Bay, Baja California Sur, Mexico

“…recruitment may be defined as the relation between the size of the spawning stock and the subsequent yearly class derived from this spawning (ricker, 1954, 1975Hilborn and Walters, 1992). the literature provides examples in which the relationship between diverse environmental factors and recruitment for different species of sardine is evident (Wada and Jacobson, 1998;Cole, 1999;guisande et al, 2001;Yatsu et al, 2005), and in which recruitment appears to oscillate, depending on the prevailing climatic conditions. For the Pacific sardine off the west coast of the Baja California peninsula, the few studies that have been performed on stock recruitment (Morales-Bojórquez, 1999, 2002Morales-Bojórquez et al, 2003) have shown that it is susceptible to the surface temperature of the sea in this zone.…”

La variabilidad climatica y las pesquerias en el Pacifico suroriental

“…En otras latitudes también existen evidencias de la existencia de regímenes ambientales Mantua, 1999aMantua, , 1999bHare & Mantua 2000, 2001Hollowed, 2001) y su efecto en los diferentes recursos pesqueros; tal es el caso de su influencia en la dinámica poblacional del lenguado del Pacífico norte ("halibut"), del "pollock" de Alaska o sardina del Pacífico norte (Theragra chalcogramma), la sardina japonesa (Sardinops melanostictus) y el lenguado de roca del Mar de Bering (Lepidopsetta bilineata), entre los más importantes, afectando los reclutamientos, procesos de denso-dependencia y patrones de crecimiento individual y poblacional (Jacobson & MacCall, 1995;Quinn & Niebauer, 1995;Hare, 1996;Francis et al, 1998;Wada & Jacobson, 1998;Walters & Wilderbuer, 2000;Clark & Hare, 2002).…”

Growth and fatness of 1975–2002 year classes of Japanese sardine in the Pacific waters around northern Japan

“…1 Annual total population abundance (all ages, available after 1977, gray and unfilled bars) and recruitment (age 0, gray bars) of Japanese sardine in Pacific waters (after Wada and Jacobson [6], Nishida et al [7]), and catch in the Pacific off the Sanriku and the eastern Hokkaido areas of northern Japan (closed diamonds and solid line)…”

“…For the total population abundance (standing stock of all ages) and the recruitment of each year class (cohort abundance at age 0), we referred to the estimates gained from the virtual population analysis performed in Wada and Jacobson [6] and Nishida et al [7]. We examined variations in both the L t at each age and the CF for different BLs with respect to population abundance and year-class recruitment among the 1975-2002 year classes.…”