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Identification of Important Habitats in Coastal New Hampshire

Chapter 20. Atlantic Silverside

The Atlantic silverside, Menidia menidia, is a small relatively common inshore fish of the mid-Atlantic coast. Silversides school in shallow estuarine waters, and are an important prey of larger fishes and birds. They are used as bait in marine recreational fisheries. The following tables are components of a model to map silverside habitat. Most of the information was derived from Fay et al. 1982 and Bigelow and Schroeder 1953. The resulting habitat scoring (suitability index values) was adjusted, based on conditions occurring at collection sites in coastal New Hampshire at which silversides were relatively abundant. Collection data were obtained from New Hampshire Fish and Game (Nelson et al. 1981), Normandeau Associates 1974, and Normandeau Associates 1995.

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 stagewould 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. Silversides typically leave estuaries in winter, so suitability was calculated for spring, summer, and fall conditions. Habitat values for the adult stages were computed as the average for the three seasons, while reproductive habitat was defined from the most favorable of either spring or summer conditions. Overall habitat was mapped from the maximum score for either adult or reproductive stages (Figures of; Adult Habitat, Spawning Habitat, Combined Life Stages).

SUBSTRATE PREFERENCES

Substrate Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition

ADULT

SPAWNING

SALINITY PREFERENCES

Salinity (ppt) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition

ADULT

SPAWNING

TEMPERATURE PREFERENCES

Temperature (C) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition

ADULT

SPAWNING

DEPTH PREFERENCES

Depth (feet, mlw*) Suitability Index: 0 to 10 scale; 0 = unsuitable, 10 = optimal condition

ADULT

SPAWNING

* mean high water approximately +8'

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