Harvesting the Wrong Fish
Stripers Forever has warned of the dangers to the striped bass population created by current management practices, which put far too much pressure on large, breeding age fish. Important scientific reports, like one by Conover and Munch from the July 2002 issue of Science Magazine, validate our concerns. Conover and Munch cite the findings of their own experiments which show that genetic changes can take place within only a few generations when the larger fish in a population are unduly pressured. Conover and Munch also point out that these genetic changes may well be irreversible, even if fishery management tactics are later corrected.
The current ASMFC-endorsed size limits for the coastal fishery that focus on large, mature fish could be altering the long-term ability of striped bass to grow to their historical size and reproductive potential. We have prepared a summary of the Conover/Munch report combined with a little history showing how the ASMFC arrived at the management plan currently in place. PDF files of the scientific reports that we quote from are available at the Stripers Forever website www.stripersforever.org
under Articles and Research.
Initially, high minimum-size regulations were used to rebuild the striped bass population after its collapse in the late 1970?s. At that time, fishing for stripers had become so unproductive that very few fishermen made the effort. Virtually all the fish caught were very large, mature specimens. When the ASMFC finally became serious about saving striped bass, the only option was to essentially stop all harvest ? and Maryland did just that. A historically high minimum size was adopted all along the Atlantic coast and gradually increased to 36 inches (at the time, it was thought that virtually all female striped bass of that size had spawned at least once).
As the fishery started to rebuild, a deal was struck - in our view to accommodate commercial interests. Called the split reference point, it essentially gave the Chesapeake Bay net fishing interests the right to harvest smaller striped bass while the coastal commercial fishery got the larger fish that the pin hookers wanted. As the population of striped bass grew, many more fishermen were attracted to the fishery. The harvest of striped bass is a fixed quota in Chesapeake Bay; officially, catches hover right around the quota, which turns out to be a number at the high end of the historic average of commercial landings. Due to widespread poaching, actual commercial catches everywhere are now well above even the official quotas. This is common knowledge, as evidenced by many arrests and convictions involving poachers with large illegal catches in possession. No estimates of this black market catch are made or counted against the commercial quota.
The coastal fishery, in terms of both recreational and commercial effort, has grown enormously since the 1980?s. The harvest is focused entirely on striped bass over 28 inches in size, and in some states the commercial size limit is even higher than that. The result is that the fishing mortality rates on these sexually mature fish have grown to well
above the ASMFC target numbers, and appear to be increasing dramatically. Many knowledgeable conservationists feel that even the target numbers are set far too high.
Because of this over exploitation, the spawning stock biomass ? the total weight of all the spawning age stripers in the population ? has been dropping for five or six years and is back to mid 1990?s levels. This is very dangerous, according to fishery scientists, because stripers are a very long-lived species. Longevity is nature?s way of insuring that the striped bass population survives the inevitable bad spawning seasons.
Some folks might think that if we wait until these fish are at least 28 inches in size ? forgetting for a second the extensive Chesapeake Bay net fishery on smaller stripers ? that we can just cut them down like a crop of corn. Isn?t it okay to remove most of the larger fish if we leave the fish less than 28 inches in size relatively undisturbed?
The answer is no, and here is why. While some female striped bass do spawn as early as five years of age, at 24 inches or so in length, these small fish carry very few eggs compared to a 45-inch striped bass that carries literally millions of eggs. The eggs in the bigger, more mature fish, in addition to being greater in number, are also larger in individual size, and therefore produce more robust fry, with better survivability, than do eggs from the smaller, younger spawners. In fact, two studies done specifically on striped bass by Monteleone and Houde, and another by Zastrow, show that the eggs of older striped bass spawners were superior in eight measures including hatchability, fry length at two different points in time, mouth gape, weight of fry, and weight of egg and its oil globule.
Setting an arbitrary measure like a 28-inch minimum size, coupled with a high fishing mortality, tends to kill a very high percentage of the genetically superior, faster growing striped bass. Since these fish are larger at an earlier age, they spend more time as legal targets for fishermen to kill; and being typically strong, aggressive specimens, they are more likely to take a bait or lure and be caught by rod and line anglers. The studies cited suggest that killing these superior stripers results in a potentially irreversible population of smaller, less robust fish. Couple this with the reduced spawning stock biomass we discussed earlier and you have a much lower quality fishery and a striper population that is easily collapsed by a few years of poor spawning success.
The comparatively large numbers of 50-pound stripers being caught today are certainly welcome, but it is a mistake to view these big fish as proof of the success of the current striped bass management scheme. These 15 to 20 year old fish were born in years when striped bass fishing mortality was nearly zero, and the fish were then well protected until they were fairly large specimens.
The sensible approach to striped bass management, according to Conover and Munch, would set a maximum rather than a minimum harvest size and apply it throughout the population. Faster growing stripers would pass more quickly than others through the gauntlet of vulnerability, and truly large, genetically superior specimens would therefore receive more protection than inferior fish.
In a conservation column in the September 2005 issue of Saltwater Sportsman Magazine, Rip Cunningham wrote the following: ?Does this mean that all fisheries should move to slot limits? Perhaps not, but it does indicate that all of the near-shore, high abundance fisheries that are of concern to recreational/personal-use anglers should be moving toward slot limit management??.
Managing the wild striped bass as a game fish by using this scientifically valid approach makes a lot more sense for the future of the resource than the current commercially-oriented system which manages stripers with the same minimum size, maximum yield ?logic? that has destroyed the ground fish populations of the North Atlantic.
Brad Burns and Duncan Barnes for Stripers Forever