ResourcesIdentification of Important Habitats in Coastal New HampshireChapter 6. Winter FlounderThe winter flounder, Pleuronectes americanus, is an important
bottom fish for commercial and recreational harvest. Populations have
declined significantly in the Gulf of Maine due to overfishing. The following
tables are components of a model to map winter flounder estuarine habitats.
The information was compiled from summaries by Buckley 1989, and
by Brown et al. (unpub.), and by examination of conditions associated
with collection sites in Great Bay and the Seabrook/Hampton estuary. The model operates on four parameters: substrate, salinity, temperature,
and depth. The model indexes the relative suitability of each environmental
parameter on a 0 to 10 basis, with 10 being optimal and 0 being unsuitable.
These suitability index values are combined by computing their geometric
mean for each grid cell in the study area. Thus, optimal habitat for any
life stage would occur where the index values were the maximum for each
of the four inputs; no value is attributed to areas where any condition
is completely unsuitable. Suitability is calculated for each season, to
accommodate annual changes in salinity and temperature. Habitats were mapped based on needs of juveniles, adults, and of reproductive
and larval stages. Winter flounder occur in New Hampshire estuaries throughout
the year and are mobile, thus able to avoid seasonally unsuitable conditions.
Accordingly, juvenile (Figure of Juvenile Habitat)
and adult (Figure of Adult Habitat) habitats were
based on the average of suitability values for each of four seasons. The
reproductive/larval (Figure of Spawning Habitat)
habitats were mapped as the maximum or most favorable score of either
winter or spring, in consideration of some flexibility in the timing of
reproduction. We noted that our winter and spring 'typical' temperature
data bracketed the conditions favorable for spawning; since optimal temperatures
must occur somewhere between the onset of winter and end of spring we
dropped temperature as a variable for the winter flounder reproductive/larval
stage. Winter flounder overall (Figure of Habitat for
Combined Life Stages) habitat was mapped as the maximum score for
either juvenile, adult, or reproductive/larval habitat. This ensures valuation
for habitats which may support stages from and into which the species
may migrate to other coastal areas. SUBSTRATE PREFERENCES Sources: Armstrong 1995, Bigelow and Schroeder 1953, Buckley 1989, Brown et al., unpub., Tort 1993, MacDonald et al. 1984. SubstrateSuitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition ADULT AND JUVENILE
REPRODUCTION, LARVAE
SALINITY PREFERENCES Sources: Brown et al., unpub., Buckley 1989, Rogers 1976, Tort 1993, Targett & McCleave 1974, MacDonald et al. 1984. Salinity (ppt) Suitability Index: 0 to 10 scale, 0 = unsuitable, 10 = optimal condition ADULT
JUVENILE
REPRODUCTION, LARVAE
TEMPERATURE PREFERENCES Sources: Brown et al., unpub., Casterlin and Reynolds 1982, Tort 1993, Buckley 1989, McCracken 1963, Van Guelpen and Davis 1979, Rogers 1976, Targett and McCleave 1974. Temperature (C) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition ADULT
JUVENILE
REPRODUCTION, LARVAE
DEPTH PREFERENCES Sources: Brown et al., unpub., Buckley 1989, McCracken 1963, Van Guelpen and Davis 1979, MacDonald et al. 1984. Depth (feet, mlw*) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition ADULT
JUVENILE
REPRODUCTION, LARVAE
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