Abiotic and biotic factors affecting recruitment variability of walleye pollock (Theragra chalcogramma) off thePacific coast ofHokkaido,Japan

Abstract

Abiotic and biotic factors affecting the recruitment variability of the Japanese Pacific stock (JPS) of walleye pollock (Theragra chalcogramma) were examined using a bivariate regression and multivariate combined model. Of the abiotic variables around Funka Bay (spawning ground), February sea surface temperature (SST) and wind direction index showed significant bivariate relationships with recruitment. February SST was positively related to recruitment, suggesting that warmer water temperature in February favors JPS recruitment. On the other hand, the relationship between February wind direction index and recruitment predicts high JPS recruitment under predominant northwest winds in February. For the biotic variables in the Doto area (nursery ground), significant and negative bivariate relationships with recruitment were observed for catch per unit effort of Kamchatka flounder (Atheresthes evermanni), Pacific cod (Gadus macrocephalus), and walleye pollock, implying an important impact of predation by these groundfishes on JPS recruitment. The overall model incorporating these abiotic and biotic factors successfully reproduced the variability in JPS recruitment. Temperature and wind conditions around the spawning ground along with predator condition in the nursery ground appear to play a dominant role in the recruitment dynamics of JPS. Based on these results and prior knowledge, we propose a new hypothesis to explain the processes controlling JPS recruitment.

Model for stock-recruitment dynamics of the Peruvian anchoveta (<i>Eugraulis ringens</i>) off Peru

“…SST has been shown to be correlated to anchovy population dynamics previously [2][3][4][5]. The impact of sea surface temperature on the recruitment dynamics of other species of fish has also been identified [6,7]. Climatic conditions such as wind direction index, North Atlantic oscillation and Southern oscillation index (SOI) have also been correlated with the dynamics and regimes of anchovy as well as other fish species [7][8][9][10][11].…”

Annual variation in otolith increment widths of walleye pollock (Gadus chalcogrammus) larvae in Funka Bay, Hokkaido, Japan

“…Kamchatka flounder (Atheresthes evermanni), Pacific cod (Gadus macrocephalus) (Yamamura et al, 1993;Yamamura, 2004) and walleye pollock larger than 300 mm in standard length (Yamamura et al, 2001(Yamamura et al, , 2002 are reported to be the major predators of walleye pollock settled juveniles in the Doto area off the Pacific coast of Hokkaido (Fig. 1), and Funamoto et al (2013) found that the predation pressure of these demersal fishes plays a dominant role in the recruitment fluctuation of walleye pollock. Yolk-sac volume and the large body size of larvae may be important factors affecting growth rate, and the nutritional condition of yolk-sac larvae could be affected by the maternal attributes of spawners (i.e., body size, age, and nutritional condition: Kjesbu et al, 1996;Solemdal, 1997;Higashitani et al, 2007).…”

“…), and Funamoto et al . () found that the predation pressure of these demersal fishes plays a dominant role in the recruitment fluctuation of walleye pollock. Yolk‐sac volume and the large body size of larvae may be important factors affecting growth rate, and the nutritional condition of yolk‐sac larvae could be affected by the maternal attributes of spawners (i.e., body size, age, and nutritional condition: Kjesbu et al ., ; Solemdal, ; Higashitani et al ., ).…”

“…Validation of daily otolith increment formation in sagittal otoliths (Nishimura and Yamada, ), feeding habits of the first‐feeding larvae (Nakatani, ) and environmental conditions during the larval stage (Nakatani, ) of this stock have been studied previously. High water temperature in February (Funamoto, ; Funamoto et al ., ), early spawning and hatching (Nishimura et al ., ; Shida, ), and favorable food availability and water temperature during the larval stage owing to delay of the Oyashio Coastal Water advection (Nakatani, ) are thought to be essential for the occurrence of the strong year classes. The growth of larval walleye pollock, as well as the prevailing oceanographic conditions and primary food availability in the western Gulf of Alaska, have been extensively studied and recruitment fluctuations have been discussed in terms of the growth‐mortality hypothesis (Bailey et al ., , ).…”

A Life Stage-based Model for Assessing the Walleye Pollock Gadus chalcogrammus Population in the East Sea

“…, , ( ) . Virtual Population Analysis (VPA) (Yabuki and Honda, 2005;Mori et al, 2012) (Shida et al, 2007;Funamoto, 2011;Funamoto et al, 2013;Funamoto et al, 2014) .…”