ResourcesIdentification of Important Habitats in Coastal New HampshireChapter 15. Rainbow SmeltRainbow smelt, Osmerus mordax, is a relatively small
freshwater and estuarine fish which is recreationally harvested during
its winter spawning migrations. There exists some commercial fishery within
Great Bay. Smelt occur from the Canadian Maritime provinces to Massachusetts.
The following tables are components of a smelt habitat model.
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 seasonal changes in salinity and temperature. It should be
noted that Great Bay has a winter ice fishery for smelt at the mouths
of several tidal tributaries; this probably constitutes a pre-spawning
aggregation downstream of suitable spawning habitats. Substrate, depth, temperature, and salinity data for the winter (January
- March) and spring (April - June) months were used to model spawning
habitat. Since the 'typical' temperature values we calculated for these
seasons bracketed the preferred values, we assumed that suitable temperatures
occur in the study area between the onset of winter and end of spring.
Therefore, we actually operated our model only on the substrate, depth,
and salinity data sets. Spawning habitat suitability values were combined
using the maximum suitability score for the winter or spring periods.
The maximum suitability score reflects the highest quality spawning habitat
available in either period (Figure of Spawning Habitat).
Substrate, depth, and temperature data for the winter, spring, summer
(July - September) and fall (October - December) months were used to model
adult and juvenile habitat. We did not find preferred salinity values
or any distinction between habitat requirements for these two life stages,
based on a review of the literature, and so used one common model. Habitat
quality for the combined juvenile and adult life stages, was computed
as the arithmetic mean of habitat suitability values for each of the 4
seasons (Figure of Adult/Juvenile Habitat).
Habitat quality for all life stages combined, was computed as the maximum
suitability score for spawning, juvenile, and adult life stages (Figure
of Habitat for Combined Life Stages). SPAWNING HABITAT PREFERENCES SUBSTRATE PREFERENCES Sources: Hulbert 1974, Crestin 1973, comments from NHF&G fishery biologists Substrate Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition REPRODUCTIVE
ADULTS, JUVENILES
SALINITY PREFERENCES Sources: Bigelow and Schroeder 1953, Crestin 1973, Clayton 1976, Murawski et al. 1980 Salinity (ppt) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition REPRODUCTIVE
ADULTS, JUVENILES We did not find information on the salinity requirements juvenile or
adult life stages, and therefore characterized habitat from substrate,
temperature, and depth parameters. These were combined using a geometric
mean. TEMPERATURE PREFERENCES Sources: McKenzie 1964, Crestin 1973, Clayton 1976. Temperature (C) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition REPRODUCTIVE
ADULTS, JUVENILES
DEPTH PREFERENCES Sources: Hulbert 1974, Bigelow Schroeder 1953. Depth (feet, mlw*) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition REPRODUCTIVE
ADULTS, JUVENILES
* mean high water approximately +8' |
