A tributary of the South Branch of the Raritan River is electrofished by the Freshwater Fisheries crew in search of trout.
An Exciting Discovery Revealed
New Jersey Division of Fish and Wildlife, along with researchers from Montclair State University, have recently revealed the true identity of the headwaters of the South Branch of the Raritan River. Such an exciting discovery is proof that first impressions can sometimes be deceiving and serves as one example of some of the remarkable findings related to the distribution and occurrence of trout now uncovered as part of a larger study being conducted throughout the inland waters of the Garden State.
Since 2001 biologists have revisited waterbodies that were first sampled 30 to 40 years ago from 1968–1972. This early effort was part of the first program designed to assess the capabilities of New Jersey’s lotic waters (streams and rivers) to support naturally reproducing trout and the presence of trout and trout-associated species. During summer base flow conditions (primarily groundwater seeping into stream channels instead of direct run off), fish populations were surveyed using electrofishing techniques at 95 sampling sites. Captured fish were identified to the species level and enumerated. This data was then used to develop the classification system that places waters into the following three categories; 1.) trout production water, used by trout for spawning or nursery purposes during their first summer of life; 2.) trout maintenance water, used for the support of trout throughout the year; 3) non-trout water, not used by trout for production or maintenance purposes. This classification scheme is part of the state’s surface water quality standards.
The section of the South Branch of the Raritan River—from its Budd Lake source down to the old YMCA Boy Scout camp dam near the intersection of River and Flanders-Drakestown roads in Mt. Olive Township—has been classified as non-trout waters since its 1968 sampling. Original survey results suggested that this part of the river only contained warmwater fish species such as sunfish, perch and bullhead. However, as a result of the latest re-inspection, approximately 2 miles of the main stem river plus six connected tributaries are now known all to contain waters of truly exceptional quality. A real potential exists for the subpopulation of brookies located there to be direct descendants of those that swam in the region’s waters upon the retreat of the last glaciation 10–15 thousand years ago!
These waters are noteworthy due to their proximity to Turkey Brook, a body of water that has demonstrated that isolated New Jersey tributaries may contain ancestral brook trout and also for the fact that a dam isolates this portion of the river from a section currently stocked, making it less likely that hatchery genes have found their way into the system. The discovery of an unknown group of New Jersey’s only native salmonid is important, for it bolsters our knowledge regarding this vital and precious natural resource. Further, consider the possibility that the new finds may be genetic relicts of a heritage strain of fish. This is a significant discovery!
To learn about other unknown or changing populations and ultimately gain a better understanding of the current condition of the state’s flowing ecosystems, previously sampled locations continue to be revisited and undergo re-inventory surveys. Among other things, like assessing overall habitat and general water quality, biologists are searching for young-of-the-year trout, also known as y-o-y. The presence of this particular age group of fish is paramount to the aforementioned stream classification system. In order for waters to attain trout production status, surveys must reveal young-of-the-year trout within the sampled section. Individuals can be any of the lotic salmonids known to inhabit New Jersey waters: brook, brown or rainbow trout. Typically trout y-o-y determination can be made during July and August by measuring fish length, which is usually less than 4 inches. If y-o-y are found, it is likely they came from parents that spawned towards the end of the previous calendar year, making these offspring less than one year old upon their summer capture.
By gathering the second set of data, biologists gain a powerful piece of information regarding changes that may have taken place over the past few decades. Related findings are very important for the presence or absence of any y-o-y trout species and provide insight into the condition of the ecosystems located in the watersheds where surveys occur.
Understanding connections of this nature are essential to managing populations of fish; trout serve as biological indicators of the overall health of not only the waters in which they inhabit, but for the surrounding lands as well.
Breeding Trout = Quality Waters
The breeding presence of trout is a strong indicator of high overall water quality and minimally impacted watersheds. In fact, in a separate but related study, work is underway that is taking a very close look at the characteristics of the landscape surrounding the survey locations. By comparing species presence or absence as related to historical and current land use percentages or total acreage, researchers seek to uncover answers as to why some populations have remained stable or why any alterations in y-o-y existence may have taken place in others.
Historic and Modern Comparisons
Regarding the re-inventory study, eighty of the original survey locations were re-sampled in the last decade or so. Serving as snapshots of overall fish populations, biologists are armed with a vast amount of information to unravel as comparisons are made between modern and historical data sets. In addition to presence and absence of species, fisheries professionals are also interested in the total composition of gathered species. Specifically, answers to numerous questions are sought, including the following:
By way of locating the presence of young-of-the-year, reproducing populations of brook trout were found at 52 of the 80 study locations at one time or another. They were present in both time frames at 31 locations, but were not found again in recent surveys on ten waters. “Losses” include surveys on the following waters; Black Brook, Dawson’s Brook, Flanders Brook, Herzog Brook, Parker Brook, Pohatcong Creek, Rinehart Brook, Shawanni Creek, Trout Brook (Middleville) and Trout Brook (Tranquility).
In these streams, brown trout have totally replaced the brooks in four instances. In three more of the losses, brook trout were found living with brown trout in the first time frame, but after the second survey only browns were sampled. In the remaining three locations that experienced brook trout losses, no young-of-the-year trout of any species were encountered in the second sampling. Changes such as these beg for answers; a few scenarios quickly come to mind.
Natural Selection in Progress
Since both species use similar niches to meet their live history needs, perhaps browns replaced brookies through outright competitive interactions. Possibly environmental conditions, such as overall water quality or suitable habitat, became degraded enough to favor brown trout, which can tolerate slightly warmer water temperatures. In the three instances where brooks were located along side browns at first and only browns were encountered at the revisit, it is remarkable to think that biologists might have been witnessing the species replacement as it was actually occurring! Loss of brook trout y-o-y presence in the second time frame is higher than either brown or rainbow trout losses.
Study results concerning brown trout show that y-o-y were located at 53 of the 80 surveys at some point during either time frame. Browns were found upon both inspections 25 times, and not found in the modern work in seven instances. It is interesting that in three losses no y-o-y of any trout species were found in the second survey. Possibly in those instances water quality decreased to a point that no salmonids could survive, or maybe individuals of other fish species were better suited to those particular locations. On the other hand, where no y-o-y of any trout species were found historically, in eight situations browns were found most recently. In total, brown trout y-o-y picked up in the second survey after not being found the first time in 21 instances.
Waters where brown trout gained a foothold after no trout y-o-y were originally found include sites on Little Brook, Macopin River, Mulhockaway Creek, Pophandusing Creek, the North Branch of the Raritan River, the South Branch of the Raritan River, Stonehouse Brook and the Whippany River. It is plausible that in these cases water quality improved to the point that brown trout were now able to survive there, but not enough to afford the same opportunity to brookies, which are known to require the coldest and cleanest systems. Regardless, our findings suggest that the range of the brown trout is expanding. Lastly, preliminary findings suggest that the loss of trout, or shift in trout species, is not correlated with the overall percent of land use changes within a specific watershed. More likely, it is the location of these changes in reference to the stream corridor resulting in poor riparian buffers, degraded in-stream habitat, and water quality that have the greatest impact to our aquatic resources. As stream corridors become more degraded, increased biological interactions (competition) with more adaptable introduced aquatic species occur resulting in further stressors.
Re-inventory: A Second Chance
The work presented here is by no means a comprehensive list of New Jersey’s trout production waters, but this subset of the large number of surveys conducted in the state each year does provide examples of the importance of field sampling. There is an old adage that states, “First impressions are important, but everyone deserves a second chance.” The headwaters of the South Branch of the Raritan River, and the numerous other instances where coldwater salmonids have been recently discovered, make a strong case for this thought to hold true for more than just people.
Much has changed in New Jersey in the last 30 or 40 years and these alterations have implications for how the state’s freshwater resources are managed. Fish and Wildlife’s fisheries professionals are working hard to keep abreast of fish population shifts, adjusting our strategies accordingly as we strive to conserve our native species and provide the best fishing possible to anglers of the Garden State.
Comparisons of reproducing trout species found at 80 stream locations, 1968–1977 vs. 2001–2010.
South Jersey Fisheries Forum
February 22, 2014; 10 a.m.
Batsto Village Visitor’s Center
in Wharton State Forest
North Jersey Fisheries Forum
Come and share your views and recommendations for the future of freshwater fisheries in New Jersey and learn about current research, management and fish culture activities!
The forum at Hackettstown will include a tour of the fish production facilities.
For more information or to pre-register (helpful, but not required) please call (908) 236-2118 or send an e-mail firstname.lastname@example.org. E-mails should include name, address, phone number and number of people attending.
Presented by NJ Department of Environmental Protection’s Division of Fish and Wildlife.
Brown trout raised at the Pequest Trout Hatchery.
Regulations in red are new this year.
Purple text indicates an important note.