Where are the cobia?
This year's cobia season is off to a very slow and late start...
This blog is a guest post by my wife, Kristen, an environmental educator for the LowCountry Institute.
Typically, these big, brown, and fast growing fish start showing up in Port Royal Sound in mid-April and by May, the season (which will last through the beginning of July or so) is in full swing. Cobia do not typically move into inshore waters – they are a near-shore species that likes to associate with wrecks and other structure. They typically spawn off beaches and at the mouths of inlets and sounds. Port Royal Sound is one of a very few locations on the East Coast where these fish venture inland. The conditions of Port Royal Sound – particularly the high salinity waters, deep channels, and abundant food (crabs are the cobia's favorite during this time of year!) – create an ideal location for spawning. So our habitat is absolutely critical to the lifecycle of these fish.
Cobia are a moderately long-lived fish, surviving at maximum 15 years in the wild. They grow quite rapidly in this time, with the SC state record cobia weighing in at 92 lbs. It takes 2-4 years for them to reach maturity; a female must reach a size of about 32 inches and males 24 inches. Legal harvest length is 33 inches; this means that smaller females may be harvested before ever having had the chance to reproduce. While the species is widely distributed around the world in tropical and subtropical waters, and there is migration up and down along the Eastern seaboard and to the Gulf, new research shows that the cobia coming into Port Royal Sound to spawn are a genetically distinct subpopulation – meaning, the fish that were spawned in our waters are the same fish that later come back to reproduce here. If we experience a local population crash, there may be very little migration from the greater cobia population to restock local fish.
The vast majority of cobia harvested in South Carolina takes place in inshore waters, mostly in Beaufort County (80-85%). Overfishing is the primary concern regarding sustainability of the cobia fishery. There is no longer a commercial fishery for cobia in the state, so all pressure is recreational and the available data about the fishery is of poor quality. Regardless of the state of the overall Atlantic cobia population (which may be healthy according to NOAA's most recent 2013 assessment), if the Port Royal Sound cobia fishery is overfished, it could cause a permanent collapse in what is arguably the most popular recreational fishery in our area. DNR's Waddell Mariculture Center has bred and released juvenile cobia into Port Royal Sound waters for the last several years and now that these fish have reached harvestable size, sampling in 2013 showed that 10% of the fish taken locally were stocked fish. All of the stocked fish were 6 years old and came from 53,000 fingerlings that were released in Port Royal Sound in 2007. Of ALL fish caught in 2013 that were 6 years old, a full 75% of those fish were from stocked brood. This should be a wakeup call regarding the state of the local cobia sub-population. Ways to alleviate negative impacts to the fishery might be a reduction of per-boat limits, a temporary closure of harvest, and/or more catch-and-release practiced by cobia fisherman. All of these actions would apply to inshore cobia only, since it appears that the Port Royal Sound cobia subpopulation is distinct from the greater Eastern seaboard cobia population. It will take the efforts of all those invested in the health of our local cobia fishery to make wise decisions to conserve these economically and ecologically important fish.