ResourcesIdentification of Important Habitats in Coastal New HampshireChapter 23. TomcodThe tomcod, Microgadus tomcod, is a small cod-like estuarine
fish which ascends tributaries of Great Bay in winter. They reside in
eelgrass or over shell beds much of the year. Tomcod are caught by anglers
incidental to the smelt fishery. The following tables are components of
a model to map their habitat. Most of the information was compiled
by Brown et al. (unpub.) from the other listed sources. The resulting
habitat scoring (suitability index values) was adjusted, based on conditions
occurring at collection sites in Great Bay at which tomcod were relatively
abundant. The model indexes the relative suitability of each of four parameters
(substrate, salinity, temperature, and depth) 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. Habitat values for adult (Figure
of Adult Habitat) and juvenile (Figure of Juvenile
Habitat) stages were computed as the average of values from each of
4 seasons, while reproductive habitat (Figure of Spawning
Habitat) was defined from the most favorable of either fall or winter
conditions. Overall habitat (Figure of Habitat for
Combined Life Stages) was mapped as the maximum score for either adult,
reproductive, or juvenile stage. SUBSTRATE PREFERENCES (all stages) Sources: Brown et al., unpub., Tort 1993, MacDonald et al. 1984, Laprise and Dodson 1990, Stewart and Auster 1987. Substrate Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition
SALINITY PREFERENCES Sources: Brown et al., unpub., Fried et al. 1973, Peterson et al. 1980, Tort 1993, Townsend 1984, Targett & McCleave 1974, MacDonald et al. 1984, Laprise and Dodson 1990, Stewart and Auster 1987. Salinity (ppt) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition ADULT
JUVENILE
SPAWNING
TEMPERATURE PREFERENCES Sources: Brown et al., unpub, Fried et al. 1973, Tort 1993, Townsend 1984, Targett & McCleave 1974, Stewart and Auster 1987. Temperature (C) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition ADULT AND JUVENILE
SPAWNING
DEPTH PREFERENCES Sources: Bigelow and Schroeder 1953, Brown et al., unpub., Laprise and Dodson 1990, MacDonald et al. 1984, Stewart and Auster 1987. Depth (feet, mlw*) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition ADULT AND JUVENILE
SPAWNING
* mean high water approximately +8' |
