scholarly journals Size-dependent predation on post-settlement winter flounder Pseudopleuronectes americanus by sand shrimp Crangon septemspinosa

2003 ◽  
Vol 263 ◽  
pp. 197-215 ◽  
Author(s):  
DL Taylor
Keyword(s):  
Winter Flounder ◽  
Pseudopleuronectes Americanus ◽  
Size Dependent ◽  
Crangon Septemspinosa

A temperature- and size-dependent model of sand shrimp (Crangon septemspinosa) predation on juvenile winter flounder (Pseudopleuronectes americanus)

2003 ◽  
Vol 60 (9) ◽  
pp. 1133-1148 ◽  
Author(s):  
David L Taylor ◽  
Jeremy S Collie
Keyword(s):  
Extreme Temperature ◽  
Winter Flounder ◽  
Interannual Variations ◽  
Pseudopleuronectes Americanus ◽  
Somatic Development ◽  
Size Dependent ◽  
Model Predictions ◽  
Dependent Model ◽  
Crangon Septemspinosa ◽  
Temporal Overlap

We investigated the temperature-mediated vulnerability of postsettled winter flounder (Pseudopleuronectes americanus) to sand shrimp (Crangon septemspinosa) predation. Small increases in flounder growth rates substantially decreased predator-induced mortality. Recent warming trends in Northwest Atlantic estuaries can increase flounder survival by accelerating growth and minimizing the duration during which juveniles are susceptible to size-dependent predation. Extreme temperature increases, however, depress growth because a disproportionate amount of energy is devoted to increased metabolism, leaving less for somatic development. Flounder survival is also reduced during warm years because of intensified shrimp predation. Moreover, interannual variations in temperature affect the relative timing of shrimp migration and flounder settlement, thus controlling the spatial and temporal overlap between predator and prey. Predicted flounder abundance and survival were statistically unrelated to observed flounder abundance sampled annually during late spring. However, model predictions and field data suggest that flounder abundance is maximal in years when seasonally averaged temperature is approximately 16 °C. Above and below this temperature, flounder year-class size is considerably lower, possibly as a result of temperature effects on trophic dynamics. We conclude that shrimp predation is a significant source of mortality for postsettled flounder, but it is not the sole determinant of interannual variations in recruitment.

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

2005 ◽  
Vol 62 (7) ◽  
pp. 1611-1625 ◽  
Author(s):  
David L Taylor ◽  
Donald J Danila
Keyword(s):  
Deterministic Model ◽  
Size Structure ◽  
Early Stage ◽  
Winter Flounder ◽  
Spawning Season ◽  
Effect Of Temperature ◽  
Feeding Rates ◽  
Pseudopleuronectes Americanus ◽  
Egg Mortality ◽  
Crangon Septemspinosa

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 Winter Flounder (Pseudopleuronectes americanus) in Long Pond, Conception Bay, Newfoundland

1971 ◽  
Vol 28 (8) ◽  
pp. 1153-1165 ◽  
Author(s):  
V. S. Kennedy ◽  
D. H. Steele
Keyword(s):  
Food Intake ◽  
Growth Rates ◽  
Plant Material ◽  
Early Growth ◽  
Winter Flounder ◽  
Pseudopleuronectes Americanus ◽  
Food Items ◽  
Fish Remains ◽  
Males And Females ◽  
Conception Bay

Monthly samples of winter flounder taken in Long Pond from November 1962 to October 1963 indicated that the flounder moved into deeper water (7–10 m) during the summer and returned to shallow water (1–2 m) from September to June. These movements corresponded to the end of the spawning season and the ripening of the gonads respectively. Spawning occurred from March until early June, most of it in May and early June. Most males were mature at age 6 and most females at age 7. Fifty percent of the males and females were mature at 21 and 25 cm respectively. The growth rates of the males and females were similar until the age of 8, after which the females apparently outgrew the males. Early growth and fecundity were similar to those reported for other areas. No feeding took place in December or January but the flounder fed in March and continued to feed throughout the summer; food intake decreased in the fall. They were omnivorous and the type of food eaten varied with the locality. Polychaetes, plant material, and molluscs were the most common food items throughout the year. Capelin eggs and fish remains were found only during a few months of the year but were eaten in great quantities.

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