Fish, Habitat and Water Quality — Making the Connection

‘No wetlands . . . no seafood.’

Most folks have seen this bumper sticker. But it could as easily read ‘no habitats . . . no seafood’ because an adequate amount of various fish habitats throughout the estuarine landscape is necessary for sustaining our fisheries in North Carolina. Generally, one habitat type is not enough. Most fish use multiple habitats over the course of their lives, and many will use more than one habitat in a single day.

Coastal habitats are vital for the state’s important fish species, as well as for fish that migrate along the East Coast. In addition to providing a home for fish, coastal habitats also increase the resilience of coastal areas to climate change and sea level rise, improve water quality, and provide valuable economic and ecological services.

Habitats and their value

North Carolina has identified six coastal habitats important to fish stocks. They are: wetlands, soft bottom, shell bottom, submerged aquatic vegetation, hard bottom, and the water column.

The water column is the habitat that connects and influences all aquatic habitats and fish. Rivers, creeks, sounds, inlets, and ocean are all distinct types of water column habitat. Environmental parameters like temperature, salinity, dissolved oxygen, and water currents directly influence the distribution of fish.

Structured habitats like wetlands, shell bottom, and submerged aquatic vegetation (seagrass), provide critical functions for fish – refuge from predators, nursery habitat for juveniles, and food. In wetlands, spot, croaker, flounder, menhaden, and penaeid shrimp are among some of the more typical juveniles, whereas in seagrass, juvenile bay scallops, shrimp, spotted seatrout, and red drum are more typical. Blue crab, sheepshead, black sea bass, hard clams, and oysters are dependent on shell bottom. In the ocean, hard bottom provides structure for reef fish. Numerous studies comparing fish use in structured habitats verses open soft bottom habitat have shown that survival, growth rates, and abundance are all greater in seagrass, shell bottom, or wetlands than in open soft bottom.

Threats

Protecting and restoring these habitats is critical for increasing our fish populations. Unfortunately, it is estimated that North Carolina has lost about 50% of its original wetlands, 90% of the historically occurring subtidal oyster rocks in Pamlico Sound and an uncertain amount of seagrass. Filling for coastal development, ditching for agriculture, and shoreline hardening have contributed to wetland loss. The decline in subtidal oyster rocks is attributed to overharvest, disease, and poor water quality. Intertidal oyster beds in upper reaches of some creeks have been silted over from runoff. Runoff is the water that flows across land and roads, draining into creeks and other waterbodies diffusely. It often transports sediment, nutrients, and bacteria into surface waters, and is a major source of water quality degradation. Because seagrass needs sufficient light to survive, runoff that increases nutrient and sediment levels in the water column has led to loss of low salinity seagrass.

Additionally, many coastal waters are impaired for various uses, such as shellfish harvest or aquatic life, due to bacteria, nutrient, or dissolved oxygen conditions. Water quality is impacted by many point sources, such as treated wastewater discharge, and nonpoint sources, such as runoff from development, roads, cropland and animal operations. Loss and degradation of these habitats reduces the overall resilience of the estuarine system and fish populations.

What’s being done to protect habitat

Recognizing the importance of protecting fish and their habitats, the North Carolina legislature passed the Fishery Reform Act in 1997, requiring the development of fishery management plans and the Coastal Habitat Protection Plan. The first Coastal Habitat Protection Plan was adopted in 2005 by the Marine Fisheries, Coastal Management and Environmental Management commissions, and staff from agencies within the Department of Environmental Quality along with a subset of members from these commissions continue to work together to draft, update, and implement the plan. The plan pulls together information on the value of different habitats to fish, their status, activities negatively influencing the condition of the habitats, and provides recommendations to protect and restore fish habitat.

Subsequent work from the Coastal Habitat Protection Plan has provided valuable information to managers. This work includes habitat assessments on Strategic Habitat Areas to prioritize the most important habitat areas to protect, implementation of coastal stormwater rules, and additional dock siting criteria to minimize impacts to seagrass and Primary Nursery Areas. The Coastal Habitat Protection Plan recommends that living shorelines be used to a greater extent for erosion control rather than bulkheads. Living shorelines are an alternative erosion control technique that incorporates a living component, like marsh plants and oysters. Research in North Carolina has shown that living shorelines effectively deter erosion, filter polluted runoff, resist storm damage, create nursery habitat, and support a higher diversity and abundance of fish and shellfish than shorelines with bulkheads. In the upcoming revision of the Coastal Habitat Protection Plan, priorities include protecting and restoring seagrasses through water quality improvements, wetland protection and enhancement using nature based methods, and habitat monitoring to assess status and regulatory effectiveness.

Coastal habitat degradation occurred from cumulative impacts over time, and it will take cumulative positive actions to protect and restore habitat and water quality conditions, and consequently improve fish populations in North Carolina.