Hope for the Future of Lake Sturgeon, by Don Orth

During the Mesozoic when the first flowering plants appeared and dinosaurs were the dominant large land animal, the ancestral sturgeon swam the waters of the ancient Tethys Sea.  This tropical body of salt water separated the supercontinent of Laurasia in the north from Gondwana in the south during much of the Mesozoic Era (251 to 65.5 million years ago). As the ancient Tethys Sea shrank and continents separated, new sturgeon species emerged. The ancestor to the North American sturgeons likely swam over 100 million years ago (Mya) in the North American Inland Sea.[1] Sturgeons have existed on our planet Earth longer than any other of the 33,000+ species of ray-finned fishes.  Further, sturgeon even persisted through the last major extinction event 66 Mya, when about 17% of all families, 50% of all genera and 75% of all species became extinct (Raup and Sepkoski 1982).

Today there are 27 species of sturgeon distributed in the Northern hemisphere. Six species in Acipenser and three species in Scaphirynchus live in North American waters.  The Lake Sturgeon Acipenser fulvescens Rafinesque 1817 has the largest distribution of any freshwater fish in North America. Lake Sturgeon can live for 100 years, grow more than 8 feet long and weigh up to 300 pounds. Instead of scales, they are protected by five rows of bony scutes along the body. Lake Sturgeon is an efficient bottom feeder with four taste-bud-filled barbels trailing from its snout as it cruises near the river or lake bottom.  Despite its common name, the Lake Sturgeon is a fluvial-dependent fish that depends on shallow, well-oxygenated flowing waters for reproduction. And like other sturgeon they jump clear out of the water. Perhaps Lake Sturgeon are communicating with other lake sturgeon as they aggregate on their breeding grounds (Sulak et al. 2002).  Imagine the characteristic acoustic signal that must be produced when a large sturgeon smacks the surface.

Distribution of Lake Sturgeon.  From Williamson (2003).

The majority of spawning runs of Lake Sturgeon have been lost. Lake Sturgeon are considered extirpated from four states, endangered in 11 states and provinces, threatened in four states and provinces, and of special concern in four states and provinces (Bruch et al. 2016a). Lake Sturgeon is approaching extinction or is extirpated in the Missouri, Ohio, and middle Mississippi river drainages.  Last year the U.S. Fish and Wildlife Service found that listing the sturgeon as threatened or endangered may be warranted. Commercial overfishing, dams and hydroelectric facilities, along with river dredging and channelization, habitat fragmentation, invasive species, and water quality deterioration are principal causes of imperilment (Bruch et al. 2016a). The slow growth and reproductive rates and the extremely high value placed on mature, egg-bearing females make sturgeon particularly vulnerable to overfishing. Their populations in lakes Erie and Ontario are less imperiled than in Minnesota, Lake Superior, the Missouri River, Ohio River, Arkansas-White River, Mississippi River, and Lake Michigan. Most states within the fish’s range provide state protection, prohibiting or limiting harvest. 

Although the U.S. Fish and Wildlife Service was to rule on the status of Lake Sturgeon, the agency missed a May 2019 deadline for determining whether the Lake Sturgeon actually warrants protection.  Consequently, the Trump Administration is being sued. The status of populations of Lake Sturgeon today reflect the interplay among place, people, and sturgeon. Spearing of Lake Sturgeon by Native American tribes fed them for thousands of years.  Spearing by Menominee people in Wisconsin occurred in spring when Lake Sturgeon migrated upstream to shallow riverine spawning grounds. In addition to being an important source of food, Lake Sturgeon is culturally and spiritually significant to tribal members. Immigrants from Europe adopted other fishing methods including spearing, netting, snag lines, and trapping, and created a short-lived, unregulated though profitable fishery. Without regulations, the yields of Lake Sturgeon from the Great Lakes peaked at 7.84 million pounds in 1879 and dropped to just 1.77 million pounds in 1899 (Bruch et al. 2016a).   Before the many values of the sturgeon were appreciated, populations were doomed with commercial extinction. 

Sturgeon spearing ice shanty in 2016.  Photo by Neil Staeck. CC BY-NC 2.0 Flickr

Today, the Winnebago System in east central Wisconsin is home to one of the largest remaining populations of naturally reproducing Lake Sturgeon in North America. The Winnebago system consists of a chain of three lakes – Winnebago, Butte des Morts, Winneconne, and Poygan – and two major inflowing river systems, the Wolf and upper Fox Rivers.   While once having incredible abundance on spawning grounds, the Lake Sturgeon of the Winnebago system was depleted and its recovery was delayed by the long controversy over spearing sturgeon in Wisconsin and several dams built between 1892 and 1926, which served as impassable barriers to upstream fish movement.  The people who settled in the Green Bay and Lake Winnebago regions were descended from French explorers who settled in the 1600s. They remained independent and relied on subsistence hunting and fishing and opposed restrictions on fishing. Gill nets, ice shanties, and spearing were permitted in Lake Winnebago long after they were banned statewide. Wisconsin imposed a statewide moratorium on sturgeon harvest in 1915 which was too late and was not to last long.

It wasn’t long after the Great Depression that regulated spearing and set line fishing was once again allowed in Lake Winnebago and upper lakes in 1932.  The minimum size limit was 30 inches and the season’s bag limit was 5. Spearing is done from ice shanties miles from shore over muddy feeding grounds. When spearing was permitted, fisheries biologist, Ed Schneberger was unable to answer questions about the size of the population, trends, or past harvest of Lake Sturgeon (Kline et al. 2009, p. 61).  In 1941, Ed Schneberger obtained information from spearers on length, weight, and sex of Lake Sturgeon harvested.  Many also shared the head of the sturgeon so the otolith could be examined for age. It turned out that many of the Lake Sturgeon harvested (ages between 14 and 40) were immature (Schneberger and Woodbury 1944).  Female Lake Sturgeon reproduce between the ages of 20 and 26 years old and fecundity increases as she grows. A record harvest of 2,828 sturgeon speared in 1958 caused concern and annual fishery assessments from 1954 to 1964 revealed the legacy of a long history of overfishing on Lake Sturgeon. In 1958, seasonal bag limit on spearing was reduced to one Lake Sturgeon.  Years later studies by Gordon Priegel of the Wisconsin DNR justified a 5% annual harvest limit. Priegel spent decades on sturgeon management and made detailed observations on sturgeon gonads that were part of the early observations used by Ron Bruch who continued to examine sturgeon gonads and the health of the spawning populations (Bruch and Binkowski 2002).

Juvenile Lake Sturgeon. Photo U.S. Fish and Wildlife Service. Source.

Lake Sturgeon did not survive in many places because of the actions of people.  The Orth principle of fish conservation optimistically states that “Passionate and persistent people who understand the fish and the place will find a way to create partnerships to conserve valued fish in perpetuity.”  But it takes time for the passionate and persistent people to come together and form lasting, trusting partnerships. The Wisconsin Lake Sturgeon Management plan was approved in 2000 (see here). Efforts to restore the Lake Winnebago populations started with formation of Sturgeon for Tomorrow led by Bill Casper and others in 1977.  Partnerships between Menominee Indian Tribes, Wisconsin Department of Natural Resources, and others were essential to restore Lake Sturgeon.  

Restoration efforts in the Menominee Indian Reservation were guided by the 1995 Menominee Reservation Lake Sturgeon Management Plan which employed stocking hatchery reared fingerlings, and transferring a small number of wild adults (~15-20 fish) per year from the lower Wolf River for release in the upper Wolf River on the Reservation (Runstrom et al. 2002). While stocking is a primary restoration strategy, for the Lake Sturgeon it would take between 20 and 40 years before initial success in terms of captured wild F1 progeny could be measured. Koenigs et al. (2018) demonstrated that the capture and transfer of adult and sub-adult Lake Sturgeon over the first 5 years worked to restore migrant spawning and resident riverine sturgeon stocks to fragmented sections of the upper Wolf River. This project was a collaborative effort with the Menominee Indian Tribe (see video).  

Sturgeon for Tomorrow has five local chapters and is the largest citizen advocacy group for sturgeon in the world. They recruit and train Sturgeon Guards to monitor spawning Lake Sturgeon throughout the spawning season from mid- to late April.    People today value the Lake Sturgeon for more reasons than consumption. Sturgeon viewing is a new activity. Each spring the spawning activities attract many fish viewers.  Visitors spent about $57 a trip on gas, food and equipment and a total of about $344,000 during the viewing season. Most have been coming back for 13 years or more to annually view sturgeon.  

Photo posted by Sturgeon for Tomorrow Facebook Group February 23, 2020. 

Scientists Bill Ballard and Fred Binkowski experimented with breeding methods and succeeded in breeding Lake Sturgeon in captivity in 1979. Many perceptive and persistent fisheries biologists followed the lead of Ed Schneberger and refined the approach to aging and stock assessment (Bruch et al. 2009).  Lake Sturgeon have been found to make sounds associated with spawning drumming sound known by local Native Americans as ‘sturgeon thunder’ (Bruch and Binkowski 2002). Regulations are better justified with appropriate harvest caps in place to reduce harvest mortality on the most fecund females.   

Methods developed for artificial propagation allowed other states to work on refilling the vacant range of Lake Sturgeon. These efforts ultimately depend on the healthy brood stock from lake Winnebago and more trusted partnerships.  Carlos Echevarria, hatchery manager at the Warm Springs Hatchery has traveled with his staff every year to collect eggs from Lake Sturgeon caught in Wisconsin’s Wolf River. Artificial breeding and captive propagation has produced founder populations for many waters that no longer have Lake Sturgeon populations. 

  

Recent efforts made by Tribal, State, Federal, and private partners have assisted toward restoring Lake Sturgeon to the Red River of the North, a place where the Lake Sturgeon is culturally and traditionally important to the Red Lake Band. Since 1998, the Tennessee Aquarium Conservation Institute has worked in partnership with the Southeast Lake Sturgeon Working Group to raise and introduce over 200,000 juvenile Lake Sturgeon back into its native range in the Tennessee River.  The Tennessee Aquarium teaches visitors about the Lake Sturgeon and anglers who catch a Lake Sturgeon can report it online.  Similar efforts to repatriate the Lake Sturgeon into its former range are underway in Georgia, Missouri, New York, and the Toledo Zoo (Dittman et al. 2015).

A juvenile lake sturgeon captured during a fisheries assessment in the St. Clair-Detroit River System. James Boase, USFWS.  Source. 

The final conservation message from the Lake Sturgeon relates to the importance of working to organize like-minded people and facilitate exchange of information.  Ron Bruch was the persistent and inspirational leader for the formation and development of the North American Sturgeon and Paddlefish Society (NASPS). The North American Sturgeon and Paddlefish Society is the North American affiliate of the World Sturgeon Conservation Society. The organization is dedicated to promoting the conservation and restoration of sturgeon species in North America by developing and advancing research pertaining to their biology, management, and utilization (Bruch et al. 2016b). The efforts of many passionate and persistent cooperators will increase the odds that Lake Sturgeon will persist for many millions of years into the future.

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[1] “…origin time for Acipenseriformes was 389.7 Mya with a 95% credibility interval of 361.5–414.2 Mya”. “The split time between sturgeons and paddlefishes is dated back to Early Jurassic at 184.4 Mya with a 95% credibility interval of 150.0–199.5Mya.” “Within the Acipenseridae clade, the divergence time between the Pacific and the Atlantic clades appears as about 121 Mya” (Peng et al. 2007)

References

Bruch, R. M., and F.P. Binkowski. 2002. Spawning behaviour of lake sturgeon (Acipenser fulvescens). Journal of Applied Ichthyology 18:570–579.

Bruch, R.M., T. J. Haxton, R. Koenigs, A. Welsh, and S. J. Kerr. 2016a. Status of Lake Sturgeon (Acipenser fulvescensRafinesque 1817) in North America. Journal of Applied Ichthyology 32(Suppl. 1):162-190.

Bruch, R.M., T.J. Haxton, and H. Rosenthal 2016b. History of the founding and early years of the North American Sturgeon and Paddlefish Society (NASPS). Journal of Applied Ichthyology 32(S1):11-14.

Bruch, R. M., S.E. Campana, S.L. Davis-Foust, M.J. Hansen, and J. Janssen. 2009. Age validation of lake sturgeon using bomb radiocarbon and known age fish. Transactions of the American Fisheries Society 138:361–371.

Dittman, D.E., M.A. Chalupnicki, J.H. Johnson, and J. Snyder. 2015. Reintroduction of Lake Sturgeon (Acipenser fulvescens) into the St. Regis River, NY: Post-release assessment of habitat use and growth.  Northeastern Naturalist 22(4):704-716.

Kline, K.S., R.M. Bruch, and F.P. Binkowski. 2009. People of the Sturgeon: Wisconsin’s Love Affair with an Ancient Fish. Wisconsin Historical Society Press, Madison, Wisconsin. 292 pp.

Koenigs, R., R. Bruch, D. Reiter, and J. Pyatskowit. 2018. Restoration of naturally reproducing and resident riverine lake sturgeon populations through capture and transfer. Journal of Applied Ichthyology 35(1):160-168.

Peng, Z., A. Ludwig, D. Wang, R. Diogo, Q. Wei, and S. He. 2007. Age and biogeography of major clades in sturgeons and paddlefishes (Pisces: Acipenseriformes). Molecular Phylogenetics and Evolution 42:854–862

Raup, D. and J. Sepkoski Jr. 1982. Mass extinctions in the marine fossil record. Science 215 (4539):1501–1503.

Runstrom, A., R.M. Bruch, D. Reiter, D., and D. Cox. 2002. Lake Sturgeon (Acipenser fulvescens) on the Menominee Indian Reservation: An effort toward co-management and population restoration. Journal of Applied Ichthyology18:481–485. https://doi. org/10.1046/j.1439-0426.2002.00426.x

Schneberger, E., and L. A. Woodbury. 1946. The lake sturgeon, Acipenser fulvescens Rafinesque, in Lake Winnebago, Wisconsin. Transactions of the Wisconsin Academy of Science, Arts, and Letters 36:131–140.

Sulak, K.J., R.E. Edwards, G.W. Hill, and M.T. Randall. 2002. Why do sturgeons jump? Insights from acoustic investigations of the Gulf Sturgeon. Journal of Applied Ichthyology 18:617-620.

Williamson, D. F. 2003. Caviar and conservation: status, management and trade of North American sturgeon and paddlefish. World Wildlife Fund. Washington, D. C.

What Are Umbrella Fish? by Don Orth

“What's an umbrella fish?” a young student asked me.  Stumped, I replied “Never heard of one.”  The question bugged me until a library search confirmed there was no “umbrella fish.”  However, in conservation biology the term ‘umbrella’ species is one of several buzzwords used for surrogate species. Surrogate species may indicate biological diversity or environmental change or simply connect in the public’s imagination regarding habitat protection. Surrogate buzzwords include focal species, indicator species, keystone species, umbrella species, target species, foundation species, flagship species, and ecological engineer species (Caro 2010).   Even if the terms are loosely used, the species-centered conservation approaches can promote public awareness and raise funds for conservation. If it works, use it. 

Flagship species are primarily intended to promote public awareness and to raise funds for conservation. While flagship species are selected for their marketing value, umbrella species are selected based on ecological criteria and are expected to benefit a wide range of co-occurring species (Caro 2010; Kalinkat et al. 2017). Is it possible to select flagship umbrellas to describe species that explicitly integrate both functions?  Perhaps. The classic giant panda (Ailuropoda melanoleuca) is a popular charismatic species used since the 1960s by World Wildlife Fund for Nature for fundraising as well as it benefits for co-occurring endemic species.  

Recently, Kalinkat et al. (2017) identified over 60 potential freshwater flagship umbrella species.  So, there could be an umbrella fish. The next phase must be to implement and evaluate conservation strategies based on the flagship umbrella species approach.  Do the flagship umbrella species attract public attention and funding for conservation?  Is the diversity of co-occurring communities protected? We don’t know.

Emmanuel Frimpong (2018) argues that our lack of knowledge perpetuates ineffectual conservation practices in tropical Afrotropical freshwater fishes. We need to understand which fishes are rare and which are common and how the species may interact in aquatic ecosystems. His experiences, studying Nocomis breeding and nest associates, confirmed that seven species of cyprinids may breed on Nocomis nests. Therefore, Nocomis may be an umbrella species, but conservation action may take time.  His story emphasizes to us all that understanding the ecology and natural history of individual species is essential to adopting the language of flagship umbrella species.  That is one thing holding us back in fish conservation efforts. Frimpong (2018) then asks “Can we protect these rare species without protecting the common species that function as their hosts?”  Probably not!

A Bluehead Chub Nocomis leptocephalus guards his breeding mound in Toms Creek, Virginia.  Photo by Emmanuel Frimpong. 

We have yet to see if the flagship umbrella species approach develops and spurs effective conservation programs.  However, the concept of an umbrella is an important one. However, the multiple individual values and motivations around fish conservation should be embraced within a large, inclusive umbrella community of conservationists.  Here I review a few of these potential umbrella fish. Remember, while umbrella species may not exist for all systems, they may be effective in some.  Therefore, the concept is important to consider further to promote conservation action.

The Humphead Wrasse Cheilinus undulatus (also known as the Napoleon Wrasse) shares habitat with a diverse community in coral reefs. The species has a broad geographic distribution in the Indo-Pacific Ocean, a region with tremendous coral reef biodiversity. Like most wrasses (Labridae), the Humphead Wrasse is a protogynous hermaphrodite, meaning they will start life as females and may transition to males. As a large, conspicuous coral reef fish that is severely overfished, it fits the criteria for a flagfish species.  Most tropical marine protected areas (MPA) are too small to effectively protect the Humphead Wrasse and a significant scaling up of MPA is required (Weng et al 2015).  Protecting the Humphead Wrasse would protect many co-occurring species with shared habitat requirements.  Therefore, it may be both a flagship and an umbrella species.

Humphead Wrasse.  Photo by Paolo Macorig.  

Asian Arowana Scleropages formosus (Müller & Schlegel, 1844) is also known as the Golden Dragonfish or Golden Arowana. These fish are so highly valued by the aquarium trade that they are seldom eaten. Yet, the native swamps and sluggish rivers in southeast Asia are highly altered and the entire aquatic ecosystem and its services are at risk.  This recognizable and charismatic fish may be an appropriate flagship umbrella species.

Asian Arowana. Photo by Marcel Bulkhead. 

The largest salmonid in the world is the highly migratory Taimen or Huchen Hucho hucho.  The Taiman, known to locals as the “river god’s daughter,” may reach up to six feet and weigh up to 200 pounds.  Overfishing and habitat change reduced populations that once thrived throughout Mongolia and Siberia (Geist et al. 2009).   Since sport anglers value the large, unique fish, the Taimen is the target species in creating a large catch-and-release fishing reserve.  Read more here.

The Arapaima is one of the largest freshwater fishes and can reach 8 feet in length.  However, throughout it range in Brazil and Guyana it seldom reaches that large size anymore due to overfishing. One of the most heavily exploited fishes in South America, even today, scientists are not certain how many species of Arapaima exist (Stewart 2013a, 2013b; Watson et al. 2016).  While it fits some requirements for a flagship species, whether it’s an umbrella species will require more studies. 

Arapaima sp.  Photo by J-subculture.com 

The Mekong river and delta regions support a highly diverse ecosystem, which is heavily dammed.  Biodiversity of the Mekong basin is second only to the Amazon basin.  New fish species are described from the Mekong regularly and no other river has so many species of very large fishes. These include giant freshwater stingray Himantura polylepis, several giant barbs (Catlocarpio saimensis and Probarbus spp), and giant catfishes.  Two catfishes, the Mekong Giant Catfish (Pangasianodon gigas) and the Striped Catfish (Pangasianodon hypophthalmus) are candidate flagship umbrella species (So et al. 2006). Fish make up ½ to 2/3^rd of the diet of rural people of the Mekong and 2/3^rd of the people are engaged in wild capture fisheries so conservation of these areas is critically important.    

Mekong Giant Catfish (left) and  striped catfish Planet Catfish (right) 

Mahseer (Tor spp; Cypriniformes: Cyprinidae) are large-bodied, migratory freshwater fishes that are endemic to the monsoonal rivers of Asia. They are flagship species because of their economic, recreational and conservation interests.  Six of eighteen species of Tor are endangered, while others are threatened or data deficient (Pinder et al. 2015). Mahseers are referred to as “kings of aquatic systems” and are the primary targets of recreational anglers.  Fishing guides and recreational anglers have a stake in the protection of the catchments that support populations of Mahseer (Bower et al. 2017), yet the value of Mahseers as umbrella species has not been assessed.

Dekkan Masheer Tor khudree  Photo by J. F. Helias 

In North America, sturgeons (Acipenseridae), American Eel, Pacific salmonids, and Brook Trout are potential flagship umbrella species.   Brook trout Salvelinus fontinalis are well studied and a variety of conservation planning tools have been developed.  Many tools designed to characterize the continuum of viability, habitat condition, and vulnerability of Brook Trout populations may also protect a wide variety of co-occurring species.   

Sturgeons and Paddlefish in North America are possible flagship umbrella species.  In 2012, the North American Sturgeon and Paddlefish Society formed to focus on “current declines in sturgeon and paddlefish populations across North America, NASPS is dedicated to promoting the conservation and restoration of these species by developing and advancing research pertaining to their biology, management, and utilization.”   There are many threats that are specific to individual species of sturgeon. While study methods are improving, conservation efforts are playing a game of catch up. Perhaps a flagship umbrella species approach can help protect essential riverine habitats for hackelbacks.    

Although the status of American Eel is unclear, but one thing is clear.  American Eels may be hindered from reaching up to 84% of upstream habitats, thereby fragmenting the single, panmictic population.  Efforts to restore connectivity may benefit a large number of co-occurring fishes.

Four species of cyprinids that are nest associates with Bluehead Chub nests.  Photo by Derek Wheaton. 

We have a difficult challenge in conserving the fishes and their habitats.  Pluralism is the rule in conservation in general and fish conservation in particular. Many approaches, many values, and many types of people must be engaged in the process (Cooke et al. 2013).  Green et al. (2015) advocated for creating a much larger community that is strengthened, rather than factionalized, by pluralistic viewpoints.  Local and large-scale activities are important to our conservation efforts.  If the concept of flagship umbrella species can assist in making conservation more effective, then we should pursue the idea vigorously.

References

Bower, S.D., A.J. Danylchuk, R. Raghavan, S. C. Danylchuk, A.C. Pinder, A.M. Alter, and S. J. Cooke. 2017.  Involving recreational fisheries stakeholders in development of research and conservation priorities for mahseer (Tor spp.) of India through collaborative workshops.  Fisheries Research 186:665-671.

Caro, T. 2010. Conservation by proxy: Indicator, umbrella, keystone, flagship, and other surrogate species.  Island Press. 

Cooke, S. J. et al. 2013. Failure to engage the public in issues related to inland fishes and fisheries: strategies for building public and political will to promote meaningful conservation. Journal of Fish Biology 83(4):997-1018.
Frimpong, E. A. 2018. A case for conserving common species. PLOS Biology 16(2): e2004261

Geist J, Kolahsa M, Gum B, Kuehn R. 2009. The importance of genetic cluster recognition for the conservation of migratory fish species: the example of the endangered European huchen Hucho hucho (L.). Journal of Fish Biology 75(5):1063-1078.

Green, S. J., J. Armstrong, M. Bogan, E. Darling, S. Kross, C.M. Rochman, A. Smyth, and D. Verissimo.    2015.  Conservation needs diverse values, approaches, and practitioners.  Conservation Letters doi: 10.1111/conl.12204

Hogan, Z.S. 2011. Ecology and conservation of large-bodied freshwater catfish: a global perspective. American Fisheries Society Symposium 77:39–53.

Kalinkat, G. and seventeen coauthors. 2017. Flagship umbrella species needed for the conservation of overlooked aquatic biodiversity.  Conservation Biology 31:481-485.

Kalinkat, G. and seventeen coauthors. 2017. Flagship umbrella species needed for the conservation of overlooked aquatic biodiversity.  Conservation Biology Supplemental file.  18 pp.

Pinder AC, Raghavan R, Britton JR. 2015. Efficacy of angler catch data as a population and conservation monitoring tool for the flagship Mahseer fishes (Tor spp.) of Southern India. Aquatic Conservation: Marine and Freshwater Ecosystems 25(6):829-838. 204

So, N., J.K. Van Houdt, and F.A. Volckaert. 2006. Genetic diversity and population history of the migratory catfishes Pangasianodon hypophthalmus and Pangasius bocourti in the Cambodian Mekong River. Fisheries Science 72(3):469-476. 237

Stewart, D. J. 2013a. Re-description of Arapaima agassizii (Valenciennes), a rare fish from Brazil (Osteoglossomorpha: Osteoglossidae). Copeia 2013:38–51.

Stewart, D. J. 2013b. A new species of Arapaima (Osteoglossomorpha, Osteoglossidae) from the Solimões River, Amazonas State, Brazil. Copeia 2013:470–476.

Watson, L.C., D.J. Stewart, and A.M. Kretzer. 2016.  Genetic diversity and population structure of the threatened giant Arapaima in southwestern Guyana: Implications for their conservation. Copeia 104:864-872.

Weng, K.C., M.W. Pedersen, G.A. Del Raye, J. E. Caselle, and A. E Gray.  Umbrella species in  marine systems: using the endangered humphead wrasse to conserve coral reefs.  Endangered Species Research 27:251-263.