Spatiotemporal trends in fish assemblages of the Mohawk River Active

Problem

The mainstem of the Mohawk River extends from Lake Delta Dam near Rome, NY downstream to its confluence with the Hudson River near Cohoes, NY. It supports a diverse fishery that is used extensively by recreational anglers.  Smallmouth bass (Micropterus dolomieu) and walleye (Sander vitreus) are among the most popular game species with anglers but past biological surveys have documented at least 56 fish species that inhabit the river. An extensive fish survey of the Lower Mohawk River was last conducted by the New York State Department of Environmental Conservation (NYSDEC) from 1979-1983. Some key findings of this research include:

 •        the river supported an abundant and fast growing smallmouth bass population

 •        anadromous blueback herring (Alosa aestivalis) were a critical forage species for the ecosystem

 •        fish communities were notably different in permanent versus seasonally impounded reaches

 •        the river received heavy angling pressure

 The river has apparently undergone many changes in the 30 years since this survey. The nonnative and invasive zebra mussel (Dreissena polymorpha), which was first observed in 1991, spread throughout the lower river by 1993. Freshwater drum (Aplodinotus grunniens) became established around 1990 and northern pike (Esox lucius) have increased in abundance as well. Meanwhile, the runs of anadromous blueback herring are becoming weaker and preliminary data suggest smallmouth bass are becoming less abundant. Finally, upgrades of the flashboards at several of the seasonal dams may allow for the repeated raising and lowering of these devices during the warm weather season to mitigate flood impacts. The extensive changes that have occurred in this ecosystem over the past 30 years warrant a comprehensive fish-community inventory to assess the current status of fish assemblages in the mainstem of the Mohawk River.

Approach

The U.S. Geological Survey (USGS) and the NYSDEC will conduct fish community surveys at a minimum of 24 locations during 2014 and 2015. The surveys will be completed using boat electrofishing of near-shore habitats. The resulting data will be analyzed to a) assess the condition of current fish assemblages, b) identify the relative abundance of common species, c) identify spatial differences associated with seasonal or permanent impoundments, and d) assess temporal changes in the fish community over the past 30 years. Field efforts will also focus on collections of American eel, blueback herring, and smallmouth bass where practical in order to obtain data and tissues needed to support collaborative research and monitoring efforts.

Preliminary Results

Analysis of data from 24 sites collected during 2014-15 indicates the Mohawk River/Barge Canal continues to support diverse fish communities. These surveys identified 39 species and suggest that the abundance and/or distribution of these species varies between permanent and seasonal impoundments. Lentic fish often associated with ponds and lakes (e.g. sunfish) were generally more abundant in the permanent impoundments while minnows were a larger component of the fish communities in seasonal impoundments. When all species were considered, mean catch per hour in permanent impoundments was approximately double that of seasonal impoundments.

 Project Location by County

Greene County, NY, Albany County, NY, Delaware County, NY, Fulton County, NY, Hamilton County, NY, Herkimer County, NY, Oneida County, NY, Lewis County, NY, Madison County, NY, Montgomery County, NY,  Fulton County, NY, Schenectady County, NY, Saratoga County, NY