Potamodromous Fishes

Potamodromy has been defined as a reproductive migration within freshwater (Myers, 1949) which includes long distance migrations of riverine fishes and migration of lacustrine fishes into tributary streams (Lagler et al., 1977). We are also using this term to describe migratory movements of fishes from the tidal Hudson River into tributary streams for spawning. We have observed ten species that are or may be potamodromous in the Hudson River (Table 15.1). Our evidence for categorizing these species as potamodromous ranges from conclusive to dubious and represents reproduction of the entire Hudson River population or a small fraction of that population. Our observations of Hudson River tributaries have been limited to the warmer parts of the year. We wish to mention the possibility that some winter spawning species, for instance Atlantic tomcod (Microgadus tomcod), may be spawning in some tributaries during a time that has never been sampled.

White sucker (Catostomus commersonii). Spring spawning runs of white sucker are well documented phenomena throughout the species' range (Geen et al., 1966; Mansfield, 1984; Smith, 1985). White sucker prefer to spawn in moderate water velocities over a gravel or rocky substrate (Scott and Crossman, 1973), habitats that are rare in the tidal Hudson River but abundant in the tributaries.

We have collected eggs and/or larvae of white sucker in fifteen out of twenty-one tributaries sampled with drift nets (Schmidt and Lake, 2000; Schmidt and Limburg, 1989; Schmidt and Stillman, 1994) from the Pocantico River (RKM 45) to the Moordener Kill (RKM 221). We have observed spawning adults in many other tributaries (Schmidt and Cooper, 1996). We have collected white sucker eggs as early as March 24 (Fishkill Creek, RKM 95.5) and collected larvae as late as June 18 (Stockport Creek, RKM 194.5). These observations indicate a lengthy spawning season that occurs in tributaries to the Hudson River. Among tributaries, there is great variation in the numbers of early life stages or adults observed. Many of these tributaries also have resident white sucker populations, which complicates the issue.

Schmidt and Limburg (1989) suggested that white sucker in the tidal Hudson River depend on tributary spawning for maintenance of the population. We concur with this suggestion based on the relative scarcity of white sucker early life

Table 15.1. Degree of potamodromy exhibited by Hudson River fishes using tributaries for spawning


Degree of potamodromy


Catostomus commersonii


Large runs in most tributaries

White sucker

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