Salt marshes have functioned as excellent protectors of shorelines against erosion for eons.  They have also acted as efficient collectors and depositories of sediments that might otherwise smother other habitats or quickly fill in estuaries and other coastal areas.  Moreover, marsh plants stabilize the transition between land and sea, and by doing so provide valuable habitat to both marine and land animals.  In fact, many marine species, including many gamefish, have come to depend on salt marshes for part or all of their life cycles.  In other words, salt marshes are an indispensable habitat in the coastal environment. With all that we know about the importance of salt marshes for sustaining healthy fisheries and healthy coastal ecosystems, you wouldn’t think we’d need convincing to keep salt marshes in a healthy state.  Unfortunately, this couldn’t be farther from the truth.  Salt marshes are under continuing threats from many sources, and threats to salt marshes are threats to gamefish.

Development in and around salt marshes and other wetlands is perhaps the most obvious impact on the health of these habitats.  Development simply wipes out the marsh by converting it to land, resulting in wholesale habitat loss.  This also removes the protection from erosion that a salt marsh naturally provides.  The measures that developers have to take to keep their new development from eroding (seawalls, riprap) further degrade the remaining shoreline habitats.  Unfortunately, some government agencies are using salt marshes as disposal areas for spoil from channel dredging, which has the same effect on the salt marsh as development (covering and filling in), and thus destroying, of salt marsh habitat.

Less obvious, but also damaging, is the digging of drainage ditches and canals to drain the water from the marsh – either for control of mosquitoes or for flood control of neighboring areas.  As should be obvious by now, salt marshes depend on tidal flushing and the mixing of salt and freshwater, and draining the marsh prevents this.  It is doubtful that apparent benefits of drainage ditches outweigh long-term negative impacts on the salt marsh communities and associated gamefish.  In fact, drainage ditches may convert low marsh into high marsh, changing the types of habitats available to gamefish and their prey.

The diversion of freshwater flows and the sediments they carry also threatens salt marshes.  Without freshwater, the high marsh deteriorates.  And without the infusion of sediments to maintain the marsh’s structural integrity, the marsh begins to erode.  The shrinking of salt marshes of the Mississippi delta has been linked to diversion of freshwater flow resulting from channelizing of the Mississippi River.  In the past, the river would deposit most of its sediments in the delta’s marshes, but now the channelized flow is so strong that sediments are carried far into the Gulf.  Without new sediments to replace portions of salt marshes that are eroding, the marshes are shrinking. Other activities that cut off normal flow of both fresh and salt water, such as impounding or damming, may have similar impacts.

Finally, while salt marshes can act as good filters of pollutants, and keep pollutants from  reaching the estuaries, pollutants can harm or even kill some of the organisms that live in the salt marsh.  For example, chemicals sprayed to kill mosquitoes can also kill invertebrates that are food for juvenile gamefish in these marshes.  Housing developments that use septic systems inject far too much nitrogen into the groundwater that flows into adjacent salt marshes.  The excess nitrogen creates blooms of algae and phytoplankton, which can cause severe depletions of oxygen when it dies and decays.  Lack of oxygen can cause rather severe die-offs of marsh organisms, including juvenile gamefish.

It should be obvious that saltwater gamefish in the warm-temperate region have an intricate relationship with salt marshes.  It should also be obvious that the degradation of salt marsh habitats has negative effects not only on the species of gamefish that we pursue with a fly rod, but on the health of coastal ecosystems.  The decisions we make now about these important coastal habitats will influence many generations of saltwater fly anglers.

All material copyright Aaron Adams 2007, 2008, and beyond, unless noted.