Wednesday, June 19, 2019

What Fish Should I Eat? by Don Orth

Fisheries and aquaculture provide protein for a quarter of the world’s population and livehoods for 59.6 million workers. Fish provide a high-quality, easily digested animal protein with essential amino acids, fats, and micronutrients. Greater consumption of fish is associated with a lower risk of dementia, cognitive decline, and cardiovascular disease (Bakre et al. 2018; Marshall and van der Meij 2018).  Eat more fish - it's good for you!  Yet, the diversity of fish and types of fishing makes the selection of what fish to eat more complicated. 
Tuna is a popular food fish worldwide.  Photo by Ashbridge Studios, CC BY-NC-ND 2.0.  Source
One of many challenges to reducing hunger and malnutrition is to eliminate overfishing and delivering seafood in sustainable manner that does not further contribute to climate change.  Globally, 67% of assessed fish stocks are within biologically sustainable levels, which means they are at or above the level associated with maximum sustainable yield (FAO 2018); however, more fish stocks are being overfished.
Global trends in the state of the world’s marine fish stocks, 1974-2015.   Source:  FAO 2018.  CC-BY-NC-SA        
Fish and fish products provide an average of only ~34 calories per capita per day but the daily contribution varies widely by region based on availability of alternative protein sources and cultural preferences for fish.  Annual per capita consumption has more than tripled since 1961 in developing regions where four fish dominate our menu — salmon, sea bass, cod, and tuna (Greenberg 2011).   Many low-income regions of Latin America and Africa, where political instability and civil unrest have stymied economic development, still have very high food deficits.

Contribution of fish to animal protein supply (2013-2015).   Source:  FAO 2018.  CC-BY-NC-SA    
More people are consuming fish than ever before. The admonition to “think global and act local” should translate to eating locally harvested seafood and minimizing costs and unsustainable fishing practices. The Code of Conduct for Responsible Fisheries (FAO 1995) is a guiding framework for implementing sustainable fisheries and aquaculture operations. It sets out international principles and standards of behavior to ensure effective conservation, management, and development of both marine and freshwater living aquatic resources. It also accounts for the impact of fishing on ecosystems, the impact of ecosystems on fisheries, and the need to conserve biodiversity.    

Sustainability is a plastic word (Nikiforuk 2019). A fishery is not simply sustainable or not sustainable.  It’s more complicated and requires many choices.  Most practitioners accept three dimensions of sustainability: social, economic and ecological, but a deeper analysis requires consideration of six dimensions of sustainable development, specifically economic, social, ecological, institutional, ethical, and technological factors (Lam and Pitcher 2012; Aquado et al. 2016). For example, justice relates to equity or the fair distribution of benefits and harm, in terms of ecosystems and social justice. Many issues play into assessing sustainability.  Globally, we should be concerned with issues of seafood safety, bycatch, fish fraud, pollution from fish farms, post-harvest loss and waste, local governance, microplastics, lost and discarded fishing gear, overharvest of forage fish harvesting for fish meal, and many other social and ethical issues. As the trade flow diagrams show us, the source of our seafood is also complicated and most regions are importing much of their seafood. Your choice of fish to eat may depend on where and how it was harvested. 
Trade flows of fish and fish product by continent, share of total imports in value 2016 (%).  Source:  FAO 2018.  CC-BY-NC-SA        
Seafood certification, or ecolabeling, provided by third-parties, such as the Marine Stewardship Council and Seafood Watch, are the beginnings of evaluation of ethical and sustainble fisheries. Fishing practices changed dramatically in response to public outrage over harvest of dolphins in tuna purse-seining.  Fisheries that meet Marine Stewardship Criteria are highly selective for the target species, have limited access, well regulated, enforced, and often involve co-management between government, scientists, and fishers.  Seafood Watch develops fisheries and aquaculture standards to judge and communicate fish to “avoid” and “good” or “best” choices.  A novel aspect of this program rates whether fisheries support human trafficking, forced labor or child labor, as well as a new tool that collects data on carbon emissions (Monterey Bay Aquarium 2018).  These third-party certifications of sustainability have not yet delivered on the promise of price premiums, improved governance, or improved environmental conditions (Roheim et al. 2018). Challenges remain in the implementation of seafood sustainability due to potential for confusion about the overlapping goals of a growing range of sustainability initiatives (McClenachan et al. 2016).  

Three types of seafood sustainability initiatives and example goals of each (McClenachan et al. 2016).
One of the remaining issues of ecosystem justice remains to be solved.  With the expansion of aquaculture, the demand for fish meal has increased.   Small fishes, menhaden, anchovies, sardines, capelin, herring, and others are harvested and sent to reduction facilities that market and sell food to fish and other farms.   These fish, often labeled as forage fish, when overfished, no longer support seabirds and larger striped bass or bluefin tuna at higher trophic levels. 

What fish should I eat?  You can eat the fish you catch locally after you learn about local fish consumption advisories.  Take time to learn more about the fish you purchase to eat and how they were harvested.  Alaska Pollock Theragra chalcogramma had the highest catch of any fish in the world, followed by anchoveta, and Skipjack Tuna Katsuwonus pelamis.   Pollock is a “best choice” option according to Seafood Watch, but the Marine Stewardship Council has certified only the US fisheries for Alaska Pollock. McDonald's Filet-O-Fish contains Alaska Pollock in North America.   Skipjack Tuna is a “best choice” if harvested by trolling or pole-and-line fisheries, whereas the long line and purse seine fisheries is a “good choice” due to concerns of bycatch of dolphins. Tuna fisheries that use purse seines with FAD (fish attraction devices) should be avoided.   How do you know?   Look for the Marine Stewardship Council logo on any fish you purchase. 
I also started to compare the carbon foot prints of wild versus farmed seafood. The Seafood Carbon Emissions Tool was created by scientists at the Monterey Bay Aquarium Seafood Watch program and Dalhousie University. This tool also allows you to calculate the emissions associated with transporting the product to its final destination.   Most highly valued species such as shrimp, prawns, salmon, tunas, groundfish (e.g., cod, hakes, and haddocks), flatfish, seabass, and seabream are traded to the most prosperous markets, while less valued species are exported to developing countries. The US imports 98% of its Atlantic Salmon.  My favorite wild Alaskan Sockeye Salmon turns out to have a very high carbon cost associated with transport  

Since aquaculture provides over 50% of global seafood and the US imports the majority of its edible seafood, expect the supply of farmed seafood to continue to increase.  Hopefully, more of these products will be marketed with third party certification to assure responsible practices. Look for the logo for Best Aquaculture Practices Certification.  Watch for locally grown seafood from farms that use recirculating aquaculture technology and integrate aquaponics with fish production.  A land-based aquaponics farm, Superior Fresh, is expanding operations in Wisconsin on a 720-acre property producing fish and leafy green vegetables.  Superior Fresh is the first land-based Atlantic Salmon producer and the world’s largest aquaponics facility.  The goal is to producing seafood with a smaller environmental footprint than other options.  At a recent Wisconsin Aquaculture conference Greg Fischer, Manager of the Northern Aquaculture Demonstration Facility, predicted that Walleye “will be the next big food fish for aquaculture in the Midwest.”  This locally produced fish would reduce demand on wild stocks. 

Aguado, S.H., I.S. Segado, and T.J. Pitcher.  2016. Towards sustainable fisheries: A multi-criteria participatory approach to assessing indicators of sustainable fishing communities: A case study from Cartagena (Spain). Marine Policy 65:97-106.
Bakre, A.T. and thirteen coauthors. 2018.  Association between fish consumption and risk of dementia: a new study from China and a systematic literature review and meta-analysis.  Public Health Nutrition 21(10):1921-1932.
FAO. 1995. Code of Conduct for Responsible Fisheries. Rome.  Accessed 17 June, 2019 from
FAO. 2018. The State of World Fisheries and Aquaculture 2018 - Meeting the sustainable development goals. Food and Agriculture Organization of the United Nations, Rome, Italy.  227 pp.  Accessed 17 June, 2019 from
Greenberg, P. 2011.  Four Fish: The Future of the Last Wild Food.    Penguin Books, 285 pp. 
Lam, M.E., and T.J. Pitcher. 2012.  The ethical dimensions of fisheries.  Current Opinion in Environmental Sustainability 4:364-373.
Marshall, S., and B. van der Meij. 2018.  Fish and omega-3 intake and health in older people.   Maturitas 115:117-118. 
McClenachan, L., S.T.M. Dissanayake, and X. Chen. 2016. Fair trade fish: consumer support for broader seafood sustainability.  Fish and Fisheries 17:825-838.
Monterey Bay Aquarium. 2018.  Monterey Bay Aquarium Seafood Watch Launches First-of-its-Kind Seafood Slavery Risk Tool.    Accessed 17 June 2019 from
Nikiforuk, A. 2019.  Against ‘sustainability’ and other plastic words.  The Tyee  2 May. Accessed on 18 June at
Roheim, C.A., S.R. Bush, F. Asche, J.N. Sanchirico, and H. Uchida. 2018. Evolution and the future of sustainable seafood market.  Nature Sustainability 1:392-398.

Friday, May 10, 2019

Walleye Madness, by Don Orth

Walleye madness makes one think about opening day of fishing on Minnesota or Canadian lakes known for their Walleye Sander vitreus.  Or perhaps the challenge of finding boat access or parking or the last dozen live minnows.    Or even the ongoing debate over what locality is the undisputed Walleye Capital of the World.   At least seven towns, perhaps more, claim to be the Walleye Capital of the World and have differing approaches to celebrating the Walleye. 

Ashley Rae displays a Walleye caught from Bay of Quinte, Ontario, Canada. Source:
Many other statues of Walleye remind us all just how important this fish is to fishing communities.  We are mad about Walleye.  It’s a popular fish and there are never enough of them to meet the demand. Many anglers, myself included, claim the Walleye is the best-tasting fish in freshwater. The sweet succulent flesh reflects the flavor of a clean healthy lake and one taste makes you begin to seek a place with an all-you-can-eat walleye night.
Willie the Walleye statue has stood along state highway 11 since 1959. 
  Baudette, Minnesota   Source
The eye of the Walleye is superbly adapted for life in weakly illuminated waters.  Adults are crepuscular or nocturnal and avoid bright light.  Walleye usually dwell near the bottoms of lakes and rivers and are a bit harder to catch.   In early morning or late evening you can catch them nearer to the water surface.   Throughout its native range, Walleye are often stocked to meet the demand because natural recruitment does not occur in many lakes and rivers to replenish fishable Walleye ―That’s the problem.  Given its popularity with anglers, the Walleye has been widely stocked outside of its native range.  Walleye are targeted as a sport fish in 34 of 50 states, and seven Canadian provinces. 

Native (gold) and non-native (maroon) range of Walleye the US.  Source: USGS.
Walleye fishing is big business. In Wisconsin, 1 in 4 residents fish and Walleye are a favorite.   In Minnesota, 1 in 3 residents fish and annual expenditures amount to $2.4 billion.  If you want to eat Walleye for dinner, you just may have to catch one yourself.   Commercial fishing is still permitted in Lake Erie, but price per pound is over $22.    Also dubbed the Walleye Capital of the World, Lake Erie is home to a $1.5 billion sport fishing industry for over two million anglers, and has what is considered world class walleye and small bass fisheries (Lucente et al. 2012).  

In treaties between Indian tribes and the federal government, tribes relinquished their rights to vast amounts of aboriginal lands in exchange for money, but they retained hunting and fishing rights.   Consequently, tribes in Wisconsin and Minnesota are entitled to a share of the walleye in ceded territories (Nelson 1990; Ovsack 1994).  Another reason there are never enough Walleye to meet all the demands.

Walleye broodstock collection from New River in March. Photo by John Copeland
Many states and provinces annually stock Walleye fry, small fingerlings (1½ –2 inches ), large fingerlings (7–8½  inches) to enhance recreational fisheries.  Virginia was a bit late in creating Walleye fisheries.  George Palmer, while a graduate student at Virginia Tech, discovered while tracking Walleye from Claytor Lake that there was a subpopulation that migrated upstream to spawn in the New River.  He analyzed the genetics of these fishes and discovered that they had a unique haplotype different than other Walleye populations (Palmer et al. 2006, 2007).   Subsequently, the Virginia Department of Game and Inland Fisheries launched a marker-assisted selection program to help identify and stock only this unique strain into the New River.

Caitlin Carey displays a Walleye collected from the New River.  Photo by John Copeland.
In early spring, typically early March, biologists sample the Walleye to select broodstock for this restoration program.  And so begins the New River Walleye madness.  Fin clips for each Walleye are excised and taken to Dr. Eric Hallerman’s Genetics Lab at Virginia Tech.  DNA is extracted and replicated to test for the presence of the unique haplotypes.    Only Walleye with the unique haplotypes will be spawned and reared for return to the New River.   
Eggs stripped from female walleye. Photo Caitlin Carey

Eggs and milt stirred with turkey feather. Photo by Caitlin Carey
 Males and females are anesthetized and eggs expressed by a gentle stroking motion from behind the gills to the vent.  Semen from males is expressed and added and eggs and semen are mixed and gently stirred with a turkey feather to keep eggs from clumping.  Fertilized eggs are hardened  and placed in incubators where they hatch in 3–7 days.  Fry are stocked in hatchery ponds where they feed on zooplankton.  First foods are small rotifers, copepod nauplii, and cyclopoid copepods,  and as they grow larger they switch to cladocerans and immature aquatic insects.   At this point, the small fingerlings have depleted the pond's plankton bloom and are ready to be stocked in Virginia waters. 
Sheila Harris extracting DNA from Walleye tissue during Walleye madness.
New River, Staunton River, and South Holston Reservoir provide the entire broodstock of Walleye for all fingerlings stocked throughout the state.   In 2018, DGIF stocked 769,544 fingerling walleyes.  There are never enough walleye to meet the demand because the time is short and hatchery propagation is expensive.  For example, Minnesota’s walleye program cost $3.7 million in 2016 (Reed and Staples 2017). Studies on factors that limit recruitment in river spawning Walleye suggest that temperature and flow may drive recruitment success (Mion et al. 1998; Gillenwater et al. 2006; Rutherford et al. 2016). In the Maumee River, as river discharge increased, the amount of suspended sediments increased, likely directly increasing larval mortality (Mion et al. 1998). Stocked Walleye have high mortality when temperatures increase within 48 hours of stocking, and smaller fingerlings are more vulnerable to thermal stress (Clapp et al. 1997).  Walleye recruitment is often reduced in warm years and in systems dominated by centrarchids and with inadequate cover for juveniles (Schiavone 1985; Santucci and Wahl 1993; Quist et al. 2003; Hoxmeier et al. 2006; Hansen et al. 2018).       
George Palmer, Biologist with Virginia Department of Game and Inland Fisheries, stocking Walleye in New River on May 8. Photo by Tom Peddy
How do we increase the number of Walleyes produced and stocked?   Michigan's statewide demand for fingerlings is 6 million per year.   Stocking practices are highly unpredictable and fingerling production varies annually.  Reed and Staples (2017) discovered that low (30 fish/littoral hectare) density stockings of small Walleye fingerlings resulted in similar Walleye abundance as high stocking rates (60 fish/littoral hectare).   Others have investigated stocking large, advanced fingerlings raised in intensive culture.  Commercial fish farmers operate in Minnesota and provide additional Walleye to lake associations for private lakes.   
Walleye stocked in New River in 2019.  Photo by Tom Peddy
Ultimately, the New River Walleye population must be enhanced to continue as a source for brood fish for statewide stocking.  Big old fat fecund female fish, or “BOFFFFs” contribute substantially to population productivity and stability in ways considerably different from smaller females (Hixon et al. 2014).  Nebraska adopted specialized regulations to protect Walleye brood stock in Sherman Reservoir. This new regulation changed from a harvest limit of four walleye with 18 inch minimum length to allowing a reduced harvest limit of two walleye within a harvest slot (15–20 inch) and one walleye more than 28 inches.   The specialized regulation increased the protection of female walleye to more than 90% and abundance of female walleye during broodstock collection doubled. (Koupal et al. 2015).

 Length frequency distribution  of walleye Sander vitreus collected during the minimum length limit (MLL; 2000–2008) and the harvest slot one over (HSO; 2009–2014) regulations at Sherman Reservoir, Nebraska. The female histogram is standardized by the total number collected with gill nets during the MLL (n = 1,504) and the HSO (n = 1,298). The male histogram is standardized by the total number collected with electrofishing during the MLL (N = 1,021) and the HSO (N = 5,895). (Koupal et al. 2017).
Fishing for Walleye can be enhanced via a variety of methods.  Once anglers are accustomed to fishing for and catching Walleye, you can be assured of continued interest in Walleye fishing.   The worldrecord Walleye was 25 pounds, from Tennessee.  The Arkansas state record was 22 lbs., 11 oz., from Greers Ferry Lake in 1982.  Anthony P. Duncan caught the Virginia state record, which as 15 pounds and 15 ounces.  The West Virginia state record was almost 19 pounds and the Georgia record was 14 pounds, 2 ounces.   Along with these trophy catches, many fine eating Walleye have been caught in Virginia and other southern waters.  But Walleye populations are sustained by annual stocking.  This effort affords many anglers the opportunity to catch Walleye, although harvest rates can prevent development of trophy Walleye fisheries (Owens et al. 2014).  In addition to the New River, you may fish for Walleye in South Holston Reservoir, Hungry Mother Lake, Flannagan Reservoir, Leesville Lake, Philpott Reservoir, Shenandoah River, Lake Brittle, Burke Lake, Lake Orange, Little Creek Reservoir, and Lake Chesdin.  While there are never enough Walleye to meet the needs, the Walleye stocking program enhances livelihoods to those who enjoy fish as food and fishing for fun.
Timmy Dixon displays a Walleye caught from New River near Fries, Virginia.  This catch would not be possible without the stocking of Walleye above Byllesby dam. 

Clapp, D.F., Y. Bhagwat, and D.H. Wahl. 1997.  The effect of thermal stress on walleye fry and fingerling mortality. North American Journal of Fisheries Management 17:429-437.
Copeland, J. R. 2017. Upper New River Walleye Management Plan 2017 to 2022. Virginia Department of Game and Inland Fisheries, Blacksburg,  Virginia. 6 pp.  
Hansen, G.J.A., S.R. Midway, and T. Wagner. 2018. Walleye recruitment success is less resilient to warming water temperatures in lakes with abundant largemouth bass populations. Canadian Journal of Fisheries and Aquatic Sciences 75:106-115.
Hixon, M.A., D.W. Johnson, and S.M. Sogard. BOFFFFs: on the importance of conserving old-growth age structure in fishery populations. ICES Journal of Marine Science 71:2171-2185.
Hoxmeier, R.J.H., D.H. Wahl, R.C. Brooks, and R.C. Heidinger. 2006. Growth and survival of age-0 walleye (Sander vitreus): interactions among walleye size, prey availability, predation, and abiotic factors.  Canadian Journal of Fisheries and Aquatic Sciences 63:2173-2182.
Johnson, B. M., M. Vogelsang, and R. S. Stewart. 1996. Enhancing a walleye population by stocking: effectiveness and constraints on recruitment. Annales Zoologici Fennici 33:577–588.
Keith D. Koupal, Jordan D. Katt, Casey W. Schoenebeck, and Brad E. Eifert. 2015. Sex-specific changes in Walleye abundance, size structure and harvest following implementation of regulations to protect broodstock. Journal of Fish and Wildlife Management 6: 448-455.
Lucente, J.E., T. Gabriel, G. Davis, C. Wellington, and F. Lichtkoppler.  2012.  Ohio’s 2010 Lake Erie Charter fishing industry.  Fisheries 37:532-541.
Mion, J.B., R.A. Stein, R. A., and EA. Marschall. 1998. River discharge drives survival of larval walleye. Ecological Applications 8: 88–103.
Nelson, K.D. 1990.  Wisconsin, walleye, and the supreme law of the land: an overview of the Chippewa Indian treaty rights dispute in northern Wisconsin.  Hamline Journal of Public Law and Policy 11:381-416.
Ovsak, C.M. 1994. Reaffirming the guarantee: Indian treaty rights to hunt and fish off-reservation in Minnesota.   William Mitchell Law Review 20:802-836
Owens, S.J., G.C. Palmer, T. Hampton, D. Wilson, and J. Harris. 2014. Differences in angler catch and exploitation of walleye from Virginia waters. Journal of the Southeastern Association of Fish and Wildlife Agencies 1:14-19.
Palmer, G.C., M. Culver, D. Dutton, B.R. Murphy, E.M. Hallerman, N. Billington, and J. Williams. 2006. Genetic analysis shows distinct walleye stocks in Claytor Lake and the upper New River, Virginia. Proceedings of the Southeastern Association of Fisheries and Wildlife Agencies 60:125–131.
Palmer, G.C., J. Williams, M. Scott, K. Finne, N. Johnson, D. Dutton, B.R. Murphy, and E.M. Hallerman, 2007. Genetic marker-assisted restoration of the presumptive native walleye fishery in the New River, Virginia and West Virginia. Proceedings of the Annual Conference of the Southeastern Association of Fisheries and Wildlife Agencies 61:17-22.
Quist, M. C., C. S. Guy, and J. L. Stephen. 2003. Recruitment dynamics of walleyes (Stizostedion vitreum) in Kansas reservoirs: generalities with natural systems and effects of a centrarchid predator. Canadian Journal of Fisheries and Aquatic Sciences 60:830–839.
Reed, J.R. and D.F. Staples. 2017. Evaluation of two different stocking rates of small walleye fingerlings in Minnesota lakes.  North American Journal of Fisheries Management 37:1243-1248.  
Santucci, V.J., Jr., and Wahl, D.H. 1993. Factors influencing survival and growth of stocked walleye (Stizostedion vitreum) in a centrarchid-dominated impoundment. Canadian Journal of Fisheries and Aquatic Sciences 50: 1548–1558.
Schiavone, A., Jr. 1985. Response of walleye populations to the introduction of the black crappie in the Indian River Lakes. New York Fish and Game Journal 32: 114–140.