Sex-specific temperature distribution in four populations of American plaice Hippoglossoides platessoides

Abstract

In the American plaice Hippoglossoides platessoides, the sexes differ in size at age in most populations, with females being larger. Because of the links between growth, ration and temperature, differences in temperature selection might be expected between the sexes in species with dimorphic growth, with the sex with the higher growth rate selecting higher temperatures. Temperature selection has also been predicted to be density-dependent in fishes, with fish occupying colder temperatures at higher levels of abundance. We examined these aspects of temperature selection in 4 populations of American plaice: the southern Gulf of St. Lawrence population and 3 populations off Newfoundland (Labrador and NE Newfoundland, Grand Bank and St. Pierre Bank). Throughout the 1970s and most of the 1980s plaice occupied cold water relative to that available in all of the areas surveyed. In all 4 populations, females tended to occupy warmer water than males. Differences between the sexes in temperature selection and in length at age both tended to be greatest in the southern Gulf population during this period. However, there was no correspondence among populations in these differences in the early 1990s, when distribution of the Grand Bank and St. Pierre Bank populations shifted sharply into warm water and the difference in temperature distribution between the sexes increased dramatically in these populations. These shifts to warmer water may be related to density-dependent effects on temperature preference. There was a strong negative relationship between the temperatures occupied by plaice and their relative abundance in the 3 Newfoundland populations but not in the southern Gulf population. Densities appear to have remained higher in the southern Gulf population than in the Newfoundland populations, suggesting that density-dependent effects on temperature preference only occur when densities fall below some threshold level.

Sexual Variation in Fisheries Research and Management: When Does Sex Matter?

“…Sexes often show a preference for different temperatures (Swain and Morgan, 2001;Hernandez et al, 2002;Wallman and Bennett, 2006) and also exhibit sex-related differences in habitat use (Price et al, 1991;Greenberg and Giller, 2001;Klemetsen et al, 2003). There is also evidence of more subtle environmental relations such as seen in the rockfish (Sebastes mystinus).…”

“…The intersexual variation that may occur with respect to relations to abiotic factors is also poorly understood. Recently, some evidence has come to light that different sexes prefer different temperatures throughout the year or seasonally (Swain and Morgan, 2001;Hernandez et al, 2002) and that sexes differ in their habitat use (Greenberg and Giller, 2001;Klemetsen et al, 2003). This field of research can be especially important when applying possible sex-related differences in temperature preference and habitat selection/identification in relation to global climate change.…”

Change in habitat associations and geographic distribution of thorny skate (Amblyraja radiata) in the southern Gulf of St Lawrence: density‐dependent habitat selection or response to environmental change?

“…, 2001). In the wild, a tendency to occupy colder temperatures at higher levels of abundance has been demonstrated for Atlantic cod ( Gadus morhua ) in the southern Gulf of St Lawrence (Swain and Kramer, 1995) and for American plaice ( Hippoglossoides platessoides ) in each of three populations off Newfoundland (Swain and Morgan, 2001). Density dependent changes in temperature preference provide an explanation for shifts in the geographic distribution of cod during their feeding season in the southern Gulf of St Lawrence (Swain, 1993, 1999; Swain and Wade, 1993).…”

Impact of environmental temperature on Atlantic cod Gadus morhua energy allocation to growth, condition and reproduction

“…The smaller reproductive investment may be because less energy is required to produce sperm than eggs (Wootton 1990). There may also be differences in energy intake and growth between sexes (Rijnsdorp & Ibelings 1989, Swain & Morgan 2001.…”