Predation on winter flounder (Pseudopleuronectes americanus) eggs by the sand shrimp (Crangon septemspinosa)

Abstract

This study estimated rates of sand shrimp (Crangon septemspinosa) predation on winter flounder (Pseudopleuronectes americanus) eggs and examined the effect of temperature on density-dependent mortality of early-stage flounder. In laboratory experiments, shrimp feeding rates on flounder eggs were positively correlated with temperature and shrimp size. Immunological assays of shrimp stomach contents indicated that 7.2% of shrimp collected from the Niantic River (Connecticut) had flounder eggs in their stomachs. Incidence of egg predation was highest in February (20%) and decreased continuously into early April (1.2%). In a deterministic model simulating predator-induced mortality of flounder eggs during a spawning season, shrimp consumed 0.4%–49.7% of the total flounder spawn. Variations in shrimp population abundance and size structure accounted for the greatest variability in egg mortality. Water temperature during the spawning season presumably alters the population dynamics of early-stage flounder. In a long-term survey, the number of yolk-sac flounder larvae in warm years (≥4.3 °C) was depressed at high egg densities, indicating strong compensatory processes that increased egg mortality and limited the abundance of larvae. Failure of flounder to produce strong year-classes of larvae during warm years, possibly resulting from altered trophic dynamics, may explain the inability of stocks to recover from previous overexploitation.

The spatial scale of phase synchrony in winter flounder (Pseudopleuronectes americanus) production increased among southern New England nurseries in the 1990s

“…Winter flounder undergo critical early life transitions during winter and spring, and high spring temperatures adversely affect the development, growth, and survival of egg, larval, and early juvenile stages (Manderson et al 2003(Manderson et al , 2006Taylor 2003a). Several studies have attributed recent declines in winter flounder abundance in SNE to warming temperatures (Oviatt et al 2003;Oviatt 2004;DNC 2007), and the negative correlation that I found between annual changes in the contribution of the age-1 fish to population estimates and spring air temperature anomalies with a 1-year time lag also indicates that early recruitment processes and temperature are strongly coupled.…”

“…Sogard et al (2001) suggested that winter flounder production was primarily controlled by factors affecting growth and mortality at fine, between-nursery spatial scales because interannual variations in the abundance of recently settled juveniles were asynchronous among three New Jersey nurseries 200 km apart. However, several investigators have suggested that recent declines in the SNE winter flounder population are related to the direct and indirect negative effects of warm spring temperatures on the growth and predation mortality of early life stages (Keller and KleinMacPhee 2000;Taylor and Collie 2003;Taylor and Danila 2005). If regional climate change is influencing nursery production, fluctuations in age-0 winter flounder abundance on nurseries may have become synchronized at coarser spatial scales.…”

Identification of marine fish egg predators using molecular probes

“…Many of the studies that have been conducted have concentrated on the role of fish as predators, but fish eggs (and larvae) are exposed to a wide spectrum of other potential predators including chaetognaths (Feigenbaum & Maris 1984), gelatinous zooplankton (Purcell 1985, Lynam et al 2005, euphausiids (Theil acker et al 1993, Krautz et al 2007) and some of the larger copepods. Obtaining direct visual evidence of consumption from some of these groups, particularly the crustacea, is difficult as they macerate their prey (Theil acker et al 1993, Taylor & Danila 2005. Finally, visual gut content analysis is a relatively labour-intensive and timeconsuming procedure.…”

“…This approach has certain advantages as the method can sometimes discriminate life-history stages, e.g. by detecting the presence of yolk proteins (Theilacker et al 1986, Taylor & Danila 2005. There are also claims that detection times in the presence of digestion may exceed DNA-based methods (Symondson 2002).…”

Windowpane flounder (Scophthalmus aquosus) and winter flounder (Pseudopleuronectes americanus) responses to cold temperature extremes in a Northwest Atlantic estuary

“…Consequently, a better understanding of what factors influence egg, larval, and young-of-year mortality has been a research priority (Van der Veer et al, 2000). Factors mediating flatfish survival at these vulnerable stages include predation (Manderson et al, 2000;Taylor and Collie, 2003;Taylor and Danila, 2005), prey availability (Leggett and DeBlois, 1994), temperature (Van der Veer, 1986;Henderson, 1998;Neuman and Able, 2009), habitat degradation (Gibson, 1994;Able, 1999;Able et al, 1999) and unsuitable hydrodynamic conditions (Rijnsdorp et al, 1985;Castillo et al, 1994). Warmer water temperatures resulting from climate change may intensify mechanisms that, either directly or indirectly, induce mortality.…”