Saltwater Fish

If you’re chasing redfish in Florida’s Pensacola Bay, you’re probably not thinking about glaciers melting in Greenland or about Atlantic coastal waters engulfing thousands of acres of tidal flats and salt marshes.

But that’s going to change. In the years ahead, those who care about fishing for spotted sea trout, grouper, snapper, tarpon, bonefish and all other saltwater species are going to think a lot about Greenland, rising sea levels, increasing ocean temperatures and expanding zones of hypoxia.

“No doubt, global warming will affect saltwater fish populations, although it’s uncertain how quickly changes will occur,” says Dr. Luiz Barbieri, director of the Marine Fisheries Research Section of the Florida Fish and Wildlife Conservation Commission. “Rising sea levels and higher salinity gradients will alter estuarine ecology, resulting in a decline or loss of critical nursery and feeding areas. Over time, rising sea levels will push salt marshes upland except in those coastal areas where substantial development has occurred.”

The loss of such critical foraging and nursery habitat will mean a dramatic reduction in algae, zooplankton and macro-invertebrates, the primary food sources for juvenile and small forage fishes. “The loss of habitat essential to fish in the early stages of their life history will impact the structure of marine communities,” says Barbieri. “The consequences of loss or degradation of nursery areas will eventually show up in the size and numbers of fishes most popular among sportsmen.”

Increased seawater temperatures will directly affect a wide range of factors critical to fishes’ survival — the availability of food, the timing and success of reproduction and migrations, and the prevalence of disease. “As yet, we don’t know how saltwater fish will adapt to a change in water temperature,” says Kenneth Haddad, the executive director of the Florida Fish and Wildlife Conservation Commission. “We do know, however, that temperature influences fish in every phase of their life cycle. The survival of a species will depend on its ability to adapt to warmer conditions.”

Based on current data regarding saltwater fish and global warming, scientific projections include the following:

• Subsequent to only a moderate increase in water temperature, changes in distribution, growth rates and recruitment success will benefit some species. Among others, large population declines and possible local extinctions may occur.

• Sea-level rise will destroy thousands of acres of coastal salt marshes and sea grass beds that are home to egg, larval and juvenile stages of game fish.

• The prevalence of disease caused by marine bacteria, fungi and parasites may increase with rising water temperatures.

• Cold-water fish will retreat from the southern boundaries of their ranges, while warm-water fish populations will expand into more northerly waters.

• Warming waters may encourage the prevalence of invasive species that compete for the prey and habitat of native saltwater game fish.

• Increasingly frequent and severe storms could disrupt feeding and nursery conditions for the eggs and larvae of game fish like snook and croaker, causing declines in recruitment. Marine species spawning offshore, such as Atlantic menhaden and blue crab, could benefit from winds that push their offspring landward.