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New Jersey

Freshwater Fishing

Freshwater Fishing

Your Stream, Your Watershed and Ways to Protect It

Photo of stream.

It is the unfortunate reality that aquatic ecosystems are one of the first to fall victim to poor land use practices and climate change. Due to continued human impacts, we know that these fragile habitats will continue to degrade unless wise decisions are made. When left unprotected, vital fish habitat is severely altered, often exceeding the biological tolerances of sensitive species.

Increases in water temperature, flood and drought frequency plus the introduction of pollutants are characteristics of these impaired systems. Whether climatic forces or a localized disturbance induces the degradation of water quality and habitat, these changes can be subtle at first and virtually invisible unless monitored closely. This was the impetus for the New Jersey Division of Fish and Wildlife to implement a project aimed to identify coldwater refugia for native Brook Trout, New Jersey's only native trout.

Like their counterpart from Europe, the Brown Trout, their need for cold, clean water and sensitivity to change makes them the ultimate bioindicator, like a canary in the coalmine. This is why in 1968, Fish and Wildlife's Bureau of Freshwater Fisheries initiated the process of identifying and classifying New Jersey waters according to their suitability to support trout. Five years later, a classification system for New Jersey waters was developed.

Although already in use by various programs within N.J. Department of Environmental Protection, Fish and Wildlife’s classification system was formally recognized in 1981 under the state's then newly adopted Surface Water Quality Standards. The Standards recognize these critical indicators of high-quality habitats, affording various protections to waters of exceptional ecological significance. New Jersey's naturally reproducing trout populations have been routinely monitored ever since.

Identifying Refuge and Impacts

Senior Biologist Scott Collenburg checking a stream temperature logger.
Senior Biologist Scott Collenburg checking a stream temperature logger.

As elevated water temperatures are a significant factor leading to the decline of native Brook Trout populations, monitoring efforts in recent years have focused on continuous temperature monitoring. Between 2018 and 2020, our Freshwater Fisheries staff has monitored summer temperatures in most locations that continue to support Brook Trout. Various metrics were employed to help understand thermal regimes and resiliency to warming of these areas.

As climate change projections predict increasing air temperatures, the effect on our state's coldwater resources is of particular concern. However, the results from this study paint a more optimistic picture for the future of Brook Trout than one might assume. Streams do not warm uniformly across space, as groundwater influences stream temperatures in headwater streams where Brook Trout are primarily found. Predicting future strongholds for Brook Trout will rely heavily on understanding the dynamics of groundwater inputs and stream temperature on a fine spatial scale.

The good news is, not all coldwater habitats should disappear, as some large-scale climate and stream models have predicted. However, this places urgency on the Division of Fish and Wildlife and our other partners throughout the state to identify and protect locations of coldwater refugia.

While temperature is considered one of the main determinants of fish distribution, it is only one piece of the puzzle in understanding how human impacts can influence the survival of our aquatic friends. Fish and Wildlife has documented temperature spikes indicative of stormwater impacts at 31 individual sites with this monitoring network. In 2019, it was determined that these patterns were significantly related to land use characteristics associated with human development. These relationships are no surprise, but we may not think about, or see, how these events affect fish.

What Do These Impacts Mean for Fish?

For instance, what happens to trout and other coldwater fish residing in a stream when a summer thunderstorm pelts the hot pavement and flows directly into your favorite trout stream? While fish have fins and can seek refuge, in many cases this opportunity does not exist due to the widespread magnitude of a warming event. This example also highlights how fish are often uniquely vulnerable to negative impacts because they are confined to aquatic habitats where movement to alternative habitats is more restricted.

Continuing the rainwater example, when Brook Trout are exposed to temperatures above 68°F, they undergo stress that can be measured at a cellular level that can ultimately affect their survival. Chronic exposure to elevated temperatures can have drastic impacts on trout and other coldwater populations. This emphasizes the importance of a strong groundwater influence in the face of rising air temperatures and the groundwater's ability to provide a more consistent cold temperature regime, helping buffer trout from the harmful effects of temperature increase.

Temperature is merely one of the many concerns of stormwater. You may be asking, what else is being carried by stormwater? That's an excellent question, but the answer is confounded based on the location, timing and length of the storm. The best-designed stormwater systems to accommodate runoff aim to make the water percolate back into the aquifer or to follow the sewer conduit system leading to a wastewater plant prior to being released into the environment. Unfortunately, most stormwater systems lead directly into streams and lakes. A host of scientists are researching these impacts to understand what is happening to fish exposed to the cocktails of pollutants or toxicants that are washed into streams with each rain event, from which fish have no means to escape.

The effects of aquatic pollution are seemingly endless, from acute mortality, to developmental issues impacting sensory organs, not to mention the impacts on humans and other wildlife when these fish are consumed. Most trout anglers can relate to the sensitivity of aquatic invertebrates such as mayflies and understand the species’ role as prey for trout, both of which are impacted by road runoff. Chloride from salt used to de-ice roads (which seems to be increasing in frequency) can wash into streams, rivers, and lakes, thereby inhibiting fish spawning.

This all sounds dire and daunting, especially at the individual level. So, what can you do as an angler, resident or neighbor looking to foster and share a healthier environment? No doubt a few questions and even some anxiety begins to bubble to the surface of our consciousness as we consider all the potential and reoccurring impacts.

Property owners can help by considering how water flows over their property and where it goes. Stormwater runoff is indeed created by surfaces that do not allow water to infiltrate into the ground, such as pavement and even highly compacted earthen surfaces. These are commonly referred to as impervious surfaces. Guides are available to help homeowners in developing a plan for their property, including recommendations such as rain gardens, rain barrels and installation of permeable hardscapes. An N.J. DEP Green Infrastructure website is found at

Here are additional actions you can take to encourage others to become more knowledgeable and to help minimize impacts on your local waterway:

  • Use fertilizer and pesticides sparingly and never before a rainstorm.
  • Mulch grass clippings into your lawn as a natural fertilizer instead of bagging them.
  • Use a low phosphorous organic fertilizer.
  • Minimize use of salt on driveways and walkways.
  • Never dump anything down a storm drain.
  • Maintain a wide, unmowed natural vegetative buffer (or mow only once a year) along any waterway, helping to slow rainwater runoff so it can permeate into the ground, trapping excess fertilizer and sediment from your lawn.
  • Plant shade trees along waterways to reduce solar input to keep the water cool.
  • Store compost, trash, firewood and other material away from any waterway.
  • Maintain your car and prevent oil leaks that may travel onto the street and into the nearest storm drain.
  • Choose to wash your car either at a car wash with a water reclaim system or at home while parked on the lawn, gravel or another permeable surface.

Take Action to Support Watershed Management

  • NJDEP offers tools for teachers to integrate watershed management into their classroom and include free classroom presentations on water pollution through the Watershed Ambassadors Program, Project WET (Water Education for Teachers), and WaterSense programs for water conservation, stormwater lessons, and publications. Visit:
  • Local watershed associations or groups are a great way to get involved locally and need volunteers to get much of their work done. Volunteering to collect water quality data, work on trails, or plant trees to shade waterways are just a few of the things you can sign up for and help protect your local watershed.
  • Take a kid fishing! There is no better way to introduce youth to the outdoors and to get them to think about being a thoughtful steward of the environment.