Patterns of Larval Emergence and Their Potential Impact on Stock Differentiation in Beach Spawning Capelin (Mallotus villosus)

Abstract

The environmental cues triggering larval capelin (Mallotus villosus) emergence in the St. Lawrence estuary and in coastal Newfoundland are different. In the estuary, emergence from the intertidal and subtidal spawning grounds starts with dusk and ends with dawn, indicating an active response to low light intensity. In the laboratory, emergence from undisturbed sediments collected in the field is perfectly synchronized with the dark phase of the illumination cycle. Nocturnal emergence would represent an adaptation reducing vulnerability to visual predators. Previous work has shown that in Newfoundland, capelin emergence from intertidal beaches is triggered by abrupt changes in water temperature following the sporadic advection to the coast of surface water masses characterized by low predator and high prey abundances. We argue that regional differences in the emergence pattern of the species represent different strategies to avoid predation at the onset of the planktonic drift when the vulnerable yolk sac larvae are densely aggregated. Selection acting on the behaviour of the early larval stages could contribute to stock differentiation in capelin.

Export production and the distribution of fish larvae and their prey in a coastal jet frontal region

“…Capelin spawn adherent Egg production in copepods can be fueled by lipid eggs on sandy intertidal flats (see Fortier et al 1987 for reserves, the immediate food supply, or a combination a review). Spawning is concentrated in the upper estuof these 2 sources of energy (Ohrnan 1987, Runge ary of the St. Lawrence (Parent & Brunel 1976), some 1988, Hirche 1989.…”

“…In all cases, egg production is 350 km upstream of the present sampling area. From accelerated by feeding and increases asymptotically late May to late June, the larvae emerge from the with phytoplankton concentration (Conover 1965, intertidal flats at night (Fortier et al 1987) and are Mullin 1988, Hirche 1989. Based on direct measureadvected seaward by the estuarine surface flow that ments of egg production, Kisrboe & Johansen (1986) later forms the Gaspe current (Jacquaz et al 1977, andKisrboe et al (1988) reported that copepod repro Fortier & Leggett 1982.…”

“…Several authors have suggested that the spawning and dispersion strategies of forage fishes such as capelin Mallotus villosus and sand lance Arnrnodytes sp. exploit the high productivity of Gaspe current surface waters (Parent & Brunel 1976, Jacquaz et al 1977, de Lafontaine et al 1984, Fortier et al 1987. In this study, we describe the distribution of phytoplankton, copepod eggs and nauplii, and fish larvae across the frontal region between the Gaspe current and the Anticosti gyre.…”

Lack of genetic divergence in capelin (Mallotusvillosus) spawning at beach versus subtidal habitats in coastal embayments of Newfoundland

“…Analysis of life-history traits suggest that capelin from the few beach spawning populations in the fjords of the northeast Atlantic are smaller, mature earlier, have smaller eggs, and are iteroparous compared with their demersal counterparts . Differences in fitness-related traits have also been reported between the two habitats in coastal Newfoundland; at the beach, eggs experienced high mortality (4%-85%) and developed faster relative to the demersal sites in the subtidal zone (Penton et al 2012), and larval emergence mechanisms that can be used to distinguish capelin stocks (Fortier et al 1987) differ between the habitats (Frank and Leggett 1982;Penton and Davoren 2008), suggesting potential for local adaptation and divergence.…”

Ritmicidade da emissão de propágulos em Chthamalus bisinuatus (Pilsbry, 1916): componentes endógenas e exógenas

“…Existe uma ampla gama de estratégias reprodutivas apresentadas pelos invertebrados, cujas pressões seletivas que as causam podem ser a facilitação da hibridização de ovos (Babcock, 1995) ou da dispersão larval (Saigusa, 1981), a prevenção de encalhamento (Vries e Forward, 1989e Ehlinger e Tankersley, 2006) ou a promoção da retenção das larvas perto do local de emissão (Basilone et al, 2006). Entretanto, o que mais se discute como sendo a principal pressão seletiva por trás da sincronia no ciclo reprodutivo é a predação, tanto da prole como dos pais (Fortier et al, 1987;Wissel e Brendl, 1988;Morgan e Christy, 1997). A sincronia na reprodução pode minimizar as perdas por predação de duas maneiras; (1) centrando os eventos de emissão de propágulos (gametas, ovos ou larvas) em períodos quando os predadores estão ausentes ou não estão se alimentando (Forward, 1987; Morgan e Christy 1994), ou (2) liberar simultaneamente um número suficiente de propágulos capaz de saciar os predadores, aumentando, então, a probabilidade de sobrevivência (Hamilton, 1971;Foster e Treherne, 1981).…”