Submitted by Brian Cowden – TU Eastern Conservation staff member
Recently I was fortunate enough to help electro fish the South Branch of the Raritan River in Mount Olive near its upper headwaters. This work, part of the Eastern Brook Trout Joint Venture, is critical to understanding the impacts of development, the impacts of non-native fish and the interaction between various populations of wild brook trout within a given watershed. Working closely with NJ Division of Fish & Wildlife, doctoral student, 4 year TIC teacher and TU member Luke Diglio has been studying the impacts of dam removal and migration patterns of native brook trout in the upper South Branch Raritan River (SBR) in Mount Olive Township. The headwaters of this important NJ trout fishery is Budd Lake, a natural, glaciated lake along rt. 46 in that township. The small dam at the outflow of Budd Lake sees warm water flow into a grassy marsh. Water temperatures are not nearly cool enough for brook trout at this outflow; however, only less than 1/4 mile downstream, the first of numerous small tributaries mixes with the lake water, cooling it down and clearing it up. Little was known until recently of this upper most stretch of the SBR until summer of 2009 when F&W fisheries biologist, Shawn Crouse joined Luke Diglio and several seasonal employees to begin electro fishing this area. Prior to these ongoing studies, this stretch was considered “Non Trout Waters” under NJ DEP Surface Waters Classifications. Both several tributaries as well as the main river channel have been sampled during summers of ‘09 and again in ‘10. The results of these studies will lead to the reclassification of this stretch of river and those tributaries that have both adult and young of the year (YOY) fish as “Trout Production Waters” which is based on the recent electro fish samples.
Segregating fish species after electro fishing
This summer, as part of his doctoral studies, Luke, overseen by NJ F&W staff biologist Shawn Crouse, has begun marking the native brook trout with a special paint designed for fisheries studies. Each brook trout sampled gets a tiny amount of this paint injected behind its skin located just behind one eye. The color of the paint as well as which eye it is placed behind is determined by the location where it was electro fished -whether that was a tributary or a section of the main stem. Each fish is then allowed to fully recover from the anesthesia given it during the process and released back to the stretch of river or tributary where it came from.
Some of the colors being used to mark brook trout in the SBR
Injecting paint into a native brook trout for study purposes
The purpose of Luke’s study is to determine if and to what extent native brook trout populations intermingle and hence, interbreed in a section of the river devoid of non-native trout such as brown and rainbow trout. Little is known about NJ brook trout and what sections of our main trout streams or tributaries are used during the year. Do fish move freely between tributaries using the main river? Do they move up into tributaries in periods of warm water? This study will allow future electro fishing of brook trout to provide those results. More than 5 tributaries have been studied as well as the main river above an impassable dam located downstream.
