For the seventh time this summer, residents of Osborne Island in Little Egg Harbor Township have confronted thousands of dead fish in their lagoon system. The most recent event was the largest, leaving portions of the Kentucky and Maryland Drive lagoon covered with dead juvenile menhaden—commonly called peanut bunker—and residents unable to escape the overwhelming odor.
The photographs prompted hundreds of comments, questions and proposed solutions. Many people asked the same fundamental question:
What is killing the fish, and why does this keep happening here?
The immediate cause appears to be low dissolved oxygen
Fish need oxygen in the water just as people need oxygen in the air. When dissolved oxygen falls too low, fish suffocate.
The New Jersey Department of Environmental Protection told NBC10 that fish kills of this type can occur when several conditions come together:
- Warm water, which naturally holds less oxygen
- Poor circulation and limited tidal flushing
- Large schools of fish entering a confined lagoon
- Biological activity and decomposition that consume the remaining oxygen
Peanut bunker travel in extremely large, tightly packed schools. They may enter a lagoon while avoiding predators and then become trapped in water that cannot supply enough oxygen to sustain them.
That is the likely immediate explanation—but it is not the end of the inquiry.
A fish kill can result from natural conditions and does not, by itself, prove that a chemical spill or toxic pollutant occurred. At the same time, recurring fish kills in the same poorly flushed lagoon should not simply be dismissed as an unavoidable act of nature. The repeated events tell us that this lagoon is particularly vulnerable and that its circulation, water quality and oxygen levels need to be studied.
How do nutrients and stormwater runoff contribute?
Excess nitrogen and phosphorus from lawn fertilizer, stormwater, pet waste, septic systems and other watershed sources can stimulate excessive algae and plant growth.
When algae and other organic material die and decompose, bacteria consume oxygen. NOAA describes this nutrient-enrichment process—known as eutrophication—as a major cause of low-oxygen water, fish kills and the loss of seagrass and other aquatic habitat.
We do not yet have sufficient water-quality data to establish how much nutrient pollution contributed to this particular Osborne Island event. However, nutrient reduction remains essential throughout the Barnegat Bay–Little Egg Harbor watershed because excess nutrients make shallow, warm and poorly circulated waters more susceptible to oxygen depletion.
Residents can help by following New Jersey’s fertilizer restrictions, avoiding fertilizer before rain, reducing turf where possible, maintaining septic systems, picking up pet waste and keeping leaves and grass clippings out of streets and storm drains.
But individual action alone cannot correct a lagoon design or circulation problem. This requires a coordinated governmental and scientific response.
What about bubblers and aeration?
Many commenters suggested installing bubblers, fountains or other aeration systems. In fact, Osborne Island residents are already taking action: approximately 16 homeowners have installed bubblers that run continuously from their docks.
These homeowners deserve credit for investing their own time and resources in an effort to improve conditions. Their experience also provides potentially useful information for evaluating how localized aeration performs within the lagoon.
However, the continuing fish kills demonstrate why individual dock-based bubblers cannot be assumed to be a complete lagoon-wide solution. The equipment may improve oxygen levels immediately around a dock, but its effectiveness depends upon its design, placement, capacity, water depth and the overall size and circulation of the lagoon. A large school of fish can also consume available oxygen far faster than small residential systems can replenish it.
A coordinated aeration system may still be part of an effective solution. Commenters have pointed to systems used in Kinsey Cove in Harvey Cedars as one possible model. That experience should be examined, but conditions there should be compared carefully with the depth, configuration, circulation and water quality of the Osborne Island lagoon.
Any larger system would need to be professionally designed and evaluated for:
- The volume of water requiring treatment
- The number, size and location of aeration units
- Electrical supply and operating costs
- Navigation and public safety
- Effects on sediment and water circulation
- Maintenance and long-term ownership
- Applicable environmental and waterfront permits
- Performance monitoring
Aeration could provide emergency protection during high-risk summer periods, but it should complement—not substitute for—better circulation, nutrient reduction and long-term water-quality management.
Would dredging solve the problem?
Dredging may also be part of a solution, particularly if accumulated sediment has reduced water depth or restricted movement at the lagoon entrance. Deeper or better-connected channels may improve circulation under some conditions.
However, dredging should not be treated as an automatic cure.
Before dredging, the responsible agencies need to determine:
- Where circulation is being restricted
- Whether sediment has accumulated at the lagoon entrance or elsewhere
- Whether increasing depth would meaningfully improve tidal exchange
- Whether deeper water could become stratified and develop low oxygen near the bottom
- Whether dredging would affect wetlands, shellfish habitat or nearby shorelines
- Whether dredged sediment is suitable for removal or beneficial reuse
- How quickly the area might fill in again
Bathymetric mapping and hydrodynamic modeling can help determine how water moves through the lagoon and whether targeted dredging would provide a lasting improvement.
Could another opening create better tidal flow?
Some residents suggested establishing another connection to surrounding waters, including a possible connection through or beneath Radio Road.
In theory, a second connection could create greater exchange and reduce the dead-end character of the lagoon. In practice, such a project could also change currents, sediment movement, salinity, flooding patterns and nearby wetlands. It would require significant engineering, environmental review, permits, property access and funding.
This concept should not be rejected without study, but neither should it be undertaken without understanding its consequences. A circulation model could compare potential alternatives—including targeted dredging, an additional connection, aeration, improvements near the lagoon mouth and combinations of these measures.
Why not simply push the fish out with a boat?
Several commenters proposed tying up a boat and running its propeller to push fish toward the lagoon entrance.
Operating a boat in this way could injure someone, damage property, disturb bottom sediment, create navigation hazards and further stress fish already struggling in low-oxygen water. It may also move dead fish into another part of the lagoon without addressing the underlying oxygen problem.
Emergency measures should be coordinated with local officials and experienced marine contractors rather than attempted independently.
Can residents remove or reuse the dead fish?
Dead fish should not be collected for food, bait, fertilizer or other personal uses. NJDEP Fish & Wildlife advises people not to handle, collect or consume dead or visibly sick fish.
Large-scale removal may be warranted when fish accumulate along private property and begin decomposing, but removal requires suitable equipment, worker protection, transportation and an approved disposal location. Responsibility and liability should be established before volunteers or contractors enter the water.
Residents should also keep children and pets away from concentrations of dead fish and visibly affected water.
Does this constitute a public-health emergency?
Low oxygen in the water is not itself a direct airborne poison, and a fish kill does not automatically mean that the water contains a harmful algal toxin or chemical contaminant.
Nevertheless, thousands of decomposing fish in an enclosed residential lagoon create legitimate health and quality-of-life concerns. Residents may experience severe odors, increased bird activity, fecal contamination around homes and docks, insects, and direct contact with decomposing wildlife and degraded water.
These concerns should be evaluated by the Ocean County Health Department in coordination with the Township and NJDEP. Water-quality testing is also important because appearance and odor alone cannot establish whether bacteria, harmful algae or another contaminant is present.
Who is responsible?
The lagoon is a man-made system, but determining legal or financial responsibility for its present condition is not as simple as identifying the original developer. Ownership, maintenance obligations, public access, easements, permits and the passage of time all matter.
What is clear is that individual homeowners cannot reasonably be expected to solve a recurring lagoon-wide environmental problem by themselves.
Save Barnegat Bay has been working with residents and Little Egg Harbor Township to pursue grant funding that could support the technical work needed to design an appropriate response. Those efforts are important, but funding alone will not resolve the problem. Meaningful inter-agency coordination and science-based investigation must occur before a preferred solution is selected.
The response should involve:
- Little Egg Harbor Township
- Ocean County
- The Ocean County Health Department
- NJDEP Fish & Wildlife
- NJDEP water-quality and coastal programs
- Residents and property owners
- Independent marine, engineering and environmental experts
What should happen next?
The first step is to replace assumptions with data. A responsible response should include:
- Continuous dissolved-oxygen and temperature monitoring during the summer, including overnight and early-morning readings when oxygen may be lowest.
- Mapping of existing residential bubblers and monitoring of oxygen levels near and beyond their effective range.
- Bathymetric mapping to identify sediment accumulation and shallow restrictions.
- Tidal and hydrodynamic analysis to measure how water enters, circulates through and leaves the lagoon.
- Water-quality sampling for nutrients, chlorophyll, bacteria and other appropriate indicators.
- Evaluation of a coordinated emergency aeration system and fish-removal protocol.
- Comparison of longer-term alternatives, including targeted dredging, improvements near the lagoon mouth, engineered aeration and possible circulation connections.
- Identification of permits, responsible entities and state, federal or county funding sources.
- A clear inter-agency response plan defining who will act when another fish kill is reported.
Residents should report active fish kills immediately to the NJDEP’s 24-hour hotline at 1-877-WARN-DEP (1-877-927-6337). Photographs, video, time, location, weather conditions and observations of fish behavior can help document the event.
A recurring warning should lead to a coordinated response
The fish may disappear with the tide and the odor may eventually fade, but that does not mean the problem has been resolved.
Four fish kills in one summer—and repeated events over multiple years—are a warning that this lagoon is not functioning well under current summer conditions. Warm weather and schooling fish may trigger an individual event, but the lagoon’s limited circulation leaves little margin for recovery when oxygen begins to fall.
Residents have already taken meaningful action, including installing and continuously operating approximately 16 dockside bubblers. They should not be left to address a lagoon-wide problem one property at a time.
The public has offered thoughtful ideas. Dredging, engineered aeration and improved tidal circulation all deserve professional evaluation. The next step is to bring the responsible agencies, residents and technical experts together, collect the necessary data and determine which combination of measures will provide a safe and lasting improvement.
Save Barnegat Bay will continue working with Osborne Island residents and Little Egg Harbor Township to seek agency assistance, technical support and grant funding. This should not become another summer in which everyone waits for the next fish kill and then asks who is responsible after the fish are already dead.
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