Fisheries provide a direct linkage between aquatic ecosystems and many human communities and provide food and commerce. How we fish matters greatly and, fortunately, there are many fishing options, including various types of nets and dredges, hook and line, traps, grappling devices, and stunning devices. One of the great challenges facing fisheries worldwide is how to minimize waste and bycatch (Davies et al. 2009). Bycatch describes the unwanted fish and other creatures caught during commercial fishing for a different species and may amount for up to 40% of world catch, according to Oceana (read more here).
The oldest fishing gears used by Chesapeake Bay watermen were fyke nets and pound nets.
Pound nets are entrapment nets that consist of a leader that interrupts the movements of target species and a heart that funnels fish into the trap, or pound. Pound nets are anchored to the bottom perpendicular to shore or in nearshore areas. Although pound nets are used today to target bluefish, flounder, catfish, or menhaden, they capture many other fish that are at historic lows, including Atlantic Weakfish and American Shad and protected species, such as Atlantic Sturgeon. In a perfect world we would have “just in time and just enough” fishing methods that produce no unwanted catch and no waste! Similarly along the Atlantic coast, trawl fisheries for herring and shrimp capture and kill every animal in the swept path and produce high levels of bycatch.
How we fish determines how much waste and bycatch occurs during harvest operations. Electrofishing is commonly used sampling method for fishery independent monitoring. Its application to commercial fishing was investigated by Richard Fitz in 1970. However, it has never become a gear permitted for commercial fishing because of concerns with interfering with recreational angling.
In a fishing trial in 2014 and 2015, the Virginia Marine Resources Commission, issued a permit to evaluate whether low-frequency electrofishing might be a viable commercial gear to target catfish in Virginia’s tidal rivers. The report was released this year summarizes the findings of this first-ever use of electrofishing for commercial harvest in Virginia waters.
George Trice and Bob Fisher (Virginia Sea Grant) with a typical haul of blue catfish
Why permit electrofishing for commercial fishing? And why now? White Catfish Amierus catus have been harvested with traditional nets from Chesapeake Bay waters for centuries. The Channel Catfish Ictalurus punctatus was first introduced in 1893 and are still widely stocked in urban fishing lakes in the watershed. Channel Catfish and White Catfish dominated commercial harvest until the 1980s. Blue Catfish Ictalurus furcatus were stocked (97,800 in Rappahannock in 1974, 1975, and 1977 and 64,100 in the James in 1975, Jenkins and Burkhead 1994, p 535) and a new and popular fishable population developed during the 1980s. Commercial and recreational fishers were catching blue catfish since the 1980s and angler interest in targeting large, trophy blue catfish accelerated in the 1990s. Flathead Catfish Pylodictis olivaris were accidentally or intentionally introduced into the James River between 1965 and 1977, and have developed a locally abundant population. The Goal Implementation Team of the Chesapeake Bay program resolved in 2011 that the “potential risk posed by blue catfish and flathead catfish on native species warrants action to examine potential measures to reduce densities and limit range expansion, and to evaluate possible negative ecological impacts.” Similarly Atlantic States Marine Fisheries Commission supported the “development of and implementation of a strategy that minimizes the population and ecological impacts of non-native invasive catfish species throughout the Chesapeake Bay watershed.”
Consequently, the Virginia Marine Resources Commission granted a commercial permit to one harvester under the supervision of Virginia Sea Grant to evaluate the use of low-frequency (<15 pps) DC electrofishing to harvest catfish from the James and Pamunkey Rivers. As expected, the harvest was significant, with an average daily catfish harvest of 3,301 pounds in 2014 and 4,462 pounds in 2015. The pilot study confirmed that this fishing method was highly selective for catfish, avoiding the problem of bycatch. The use of a chase boat to follow the boat generating the electric field was most efficient. Also the use of large metal-mesh dip nets minimized snagging on pectoral or dorsal fins. The trial resulted in the harvest of all sizes of catfish, including many in excess of 15 pounds. Processors, however, preferred fish between 3-8 pounds.
Virginia Department of Game and Inland Fisheries using electrofishing to collect blue catfish
Will electrofishing become a new harvest technique for Virginia watermen? There are still a number of issues of concern. Obviously, the biggest concern is from those now harvesting catfish with traditional nets, traps, or hook and line. The user conflicts (both real and imagined) have yet to be fully evaluated. Second, additional permits will have to be limited and VMRC has not previously dealt with limiting entry to commercial fishing. Third, the use of low-frequency electrofishing is limited to water temperatures > 18 C (Bodine and Shoup 2010). Consequently, harvest of catfish during the warmer months overlaps with harvest of farmed catfish from southern states. This means catfish prices are lower than during winter. Fourth, electrofishing effectiveness decreases in water with conductivity that exceeds the internal conductivity of the fish (Miranda and Dolan 2003), and electrofishing can be ineffective in brackish waters (Bringolf et al. 2005). Therefore, the harvest of catfish from mesohaline and polyhaline areas will continue to rely on traditional methods. Finally, recreational fishers prefer large size catfish for catch and release and intense unrestricted harvest of catfish will truncate the size distribution and limit trophy catch (Bonvecchio et al. 2011).
Blue Catfish have dispersed and established populations in the Potomac River and other Maryland tributaries. Therefore, the harvest of catfish is a regional issue; recently the Maryland DNR was granted authority to regulate trotlines for catfish harvest. Will Maryland watermen also wish to adopt low-frequency DC electrofishing?
The electrofishing catfish harvest trials provide a possible tool for managing the abundance and size of Blue Catfish and Flathead Catfish. There are more questions to answer. Can we collapse the blue catfish? Do we want to?
George Trice using electrofishing gear to harvest blue catfish (from Trice and Balazik 2016).
Bodine, K. A., and D. E. Shoup. 2010. Capture efficiency of blue catfish electrofishing and the effects of temperature, habitat, and reservoir location on electrofishing-derived length structure indices and relative abundance. North American Journal of Fisheries Management 30(2): 613-621.
Bonvechio, T.F., M.S. Allen, D. Gwinn, and J.S. Mitchell. 2011. Impacts of electrofishing removals on the introduced flathead catfish population in the Satilla River, Georgia. American Fisheries Society Symposium 77:395-407.
Bringolf, R. B., Kwak, T. J., Cope, W. G., and M.S. Larimore. 2005. Salinity tolerance of flathead catfish: implications for dispersal of introduced populations. Transactions of the American Fisheries Society 134(4): 927-936.
Davies, R., Cripps, S., Nickson, A., and Porter, G. 2009. Defining and estimating global marine fisheries bycatch. Marine Policy, doi:10.1016/ j.marpol.2009.01.003.
Fitz, R. 1970. Potential of electrofishing gear for freshwater commercial fish harvest. Progressive Fish-Culturist 32(2):105-109.
Jenkins, R.E., and N.M. Burkhead. 1994. Freshwater fishes of Virginia. American Fisheries Society, Bethesda, Maryland. 1079 pp.
Miranda, L. E., & Dolan, C. R. (2003). Test of a power transfer model for standardized electrofishing. Transactions of the American Fisheries Society 132(6): 1179-1185.
Trice, G.E., IV, and M. Balazik. 2016. Testing experimental collection gears to increase harvest efficiency of the electrofishing fishery targeting introduced blue catfish in Virginia waters. Final Report of Fishery Resource Grant Project 2015-01. 18pp.