Tuesday, January 31, 2017

Puzzling Over Large Aggregations of Sharks, by Don Orth

Ecological principles should guide the wise use and management of fisheries. However, occasionally it appears at first glance that some principles don't apply. My example today is the extreme inverted pyramid.  Animal ecologist, Charles S. Elton,  introduced the pyramid of numbers in 1927 and coined the term “food chain.”  Later we would adopt the term “food webs” (May 1983).  But Eltonian pyramids would remain as characteristics of ecosystems. Pyramids of numbers and biomass were replaced by energy pyramids (Lindeman 1942) where organism biomass is constrained into rigidly delineated trophic levels. Early work by Elton and Lindeman did not include coral reef ecosystems; however, recently investigators have revealed the shapes of pyramids in coral reef ecosystems where shark are apex predators.
Gray Reef Shark Carcharhinus amblyrynchos was one of several sharks studied by Mourier et al. (2016). Photo by Albert Kok  Source
Basically, energy pyramids graphically depict the declining energy as one moves up the trophic levels in a community.  The producers derive and transfer energy from nonliving sources into the biotic community. 
(i) Bottom-heavy pyramids of numbers (N), (ii) bottom-heavy pyramid of biomass (B), and  (iii)   inverted biomass pyramid.  From Tribelco et al. (2013).
Elton observed a strong relation between the trophic level organisms in food chains and their body sizes.   Consequently, we would expect to see a decline in biomass (abundance) with corresponding increase in body mass.  This is called the biomass size spectrum. It makes intuitive sense and complies with the laws of thermodynamics.  Numerous investigators have explored the application of the biomass spectrum to identify constraints on the structure of aquatic communities and as an indicators of perturbation (Jung and Houde 2005; Sprules and Barth 2016).      
Example biomass size spectrum    Source
A recent investigation of a biosphere reserve located in French Polynesia, largely protected from human influences, revealed a unique energy pyramid and size spectrumInvestigators used a series of video-assisted underwater visual census surveys across the entire shark school to provide precise estimates of shark numbers.  Here the density of apex predator, the Gray Reef Shark, averaged of 600 reef sharks, two to three times the biomass per hectare documented for any other reef shark aggregations!  Imagine 14 to 40 sharks per hectare.  It is unexpected for the largest apex predators to be so abundant. 
Gray Reef Shark aggregations in Fakarava Pass, in the Tuamotu Archipelago of French Polynesia.   Source: Mourier et al. (2016).
So, how is it that we observe cases of extreme inverted pyramids?  The extreme reef shark densities do not make ecological sense.  The observation was made in a biosphere reserve where human impact was negligible.  Is this what we expect in pristine reefs?

This large shark aggregation would need 147-350 kg of fish per day --  that is 91 tonnes per year. Yet, the fish production is only 17 tonnes per year.  The math doesn't work here.  The extreme inverted pyramid is a paradox.  It cannot exist, unless there is a subsidy from outside the area.  Either the sharks move out of the area to feed or else fish enter the area from elsewhere and become shark food.   Investigators tagged the sharks and tracked their movements.  Predators typically make foraging excursions to enable them to feed on multiple pyramids.  However, that was not the whole story.
Examples of shark foraging in the pass at night on the Camouflage Grouper Epinephelus polyphekadion (A, B, and C) and the Whitemargin Unicorn fish Naso annulatus (D).  Source:  Mourier et al. (2016)
What Mourier et al. (2016) discovered were large aggregations of groupers (17,000 were counted in one aggregation) that moved into the area during the grouper spawning season.  This migration brought in 31 tonnes of shark food that was produced elsewhere.  Other fish also migrate in large aggregations, thereby transferring fish production from elsewhere.  These spawning aggregations provide the energy subsidies needed to support large aggregations of sharks.  When the spawning aggregations became scarcer, the sharks shifted to making foraging excursions.  For a quick video review of this work, click here

The full potential of the size spectrum theory approach linked to energy pyramids has yet to be realized as more studies must be done from a wide range of ecosystems (Tribelco et al. 2013).  It is a data-hungry approach, but few worthwhile scientific investigations are data free.  Our challenge is finding study regions not heavily influenced by the removal of the top predators. 

This story about super abundant shark aggregations and their reliance on spawning aggregations of groupers for energy subsidies is an important discovery for fisheries management.  It illustrates the futility of single species fisheries management.  Sharks cannot be managed via harvest regulations alone.  Even if no sharks were harvested from this population, the population may decline depending on conditions for other fishes outside the biosphere reserve. Conservation of fish spawning aggregations, which are often targets of exploitation (Sadovy and Domeier 2005), can help conserve shark populations, especially if combined with shark fishing bans.  Simpfendorfer and Heupel (2016) emphasized the critical need for managers to protect the areas over which the sharks disperse to feed, which requires a better understanding of the movement patterns to inform management plans.  Fisheries managers cannot draw boundaries in open ecosystems without knowing the actual movement patterns of all elements of the community.    

Elton, C. S. 1927. Animal Ecology. The Macmillan Company, New York. 260 pp.
Jung, S., and E.D. Houde. 2005.    Fish biomass size spectra in Chesapeake Bay. Estuaries 28:226-240.
Lindeman, R. L., 1942. The trophodynamic aspect of ecology. Ecology 23: 399–418.
May, R. M. 1983. The structure of food webs. Nature 301: 566–568.
Mourier, J., J. Maynard, V. Parravicini, L. Ballesta, E. Clua, M.L. Domeier, and S. Planes.  2016.  Extreme inverted trophic pyramid of reef sharks supported by spawning groupers.  Current Biology 26(15):2011-2016.  DOI: http://dx.doi.org/10.1016/j.cub.2016.05.058
Sadovy, Y., and M. Domeier. 2005.  Are aggregation-fisheries sustainable? Reef fish fisheries as a case study. Coral Reefs 24:254. doi:10.1007/s00338-005-0474-6
Simpfendorfer, C.A., and M.R. Heupel.  2016.  Ecology: The upside-down world of coral reef predators.  Current Biology 26:R701–R718,
Sprules, W.G., and L.E. Barth. 2016.  Surfing the biomass size spectrum: some remarks on history, theory, and application.  Canadian Journal of Fisheries and Aquatic Sciences 73(4): 477-495, 10.1139/cjfas-2015-0115
Trebilco, R., J.K. Baum, A.K. Salomon, and N.K. Dulvy.   2013.  Ecosystem ecology: size-based constraints on the pyramids of life.  Trends in Ecology & Evolution 28(7):423-431.

Thursday, January 26, 2017

Shades of Gray Snapper, by Don Orth

Gray Snapper Lutjanus griseus is a very common snapper in the Atlantic and Caribbean.  It goes by two common names, Gray Snapper and Mangrove Snapper, but neither appears to be totally accurate. The Gray Snapper is more than its lackluster name may imply.   It is a member of the Lutjanidae family that includes over 100 species distributed throughout the Atlantic, Indian, and Pacific oceans and associated with reef environments.  Snapper are characterized by a continuous dorsal fin and canine teeth.  Yes, they look like dog teeth! There is even a species called the Dog Snapper Lutjanus jocu   The Gray Snapper has an emarginate caudal fin, rounded anal fin, and the dorsal and caudal fins have dark or reddish borders. 

The Gray Snapper is not always gray colored. "Lutjanus" is Latin for “snapper.” And the species name, "griseus," means "gray."  Gray Snapper was named in 1758 by Carl Linnaeus and the specimen used by Linnaeus to describe the species as “griseus” was old and gray. Like many fishes, color pattern alone may not be the most reliable way to a positive identification. Rather the color of the Gray Snapper is variable, sometimes grayish-red, sometimes grayish green or dusky olive on the back and sides. On occasion they may appear bright brick red or copper red.  The young are most variable.  Often young specimens have a dark strip from snout through the eye to the upper opercle and a less distinctive thin blue wavy line on the cheek below the eye. Sometimes the flanks are gray but interspersed with brick red spots on each scale, especially among the offshore and larger.  Sometimes, noticeable vertical bars are displayed on their sides.  See photos for varieties.
Juvenile Gray Snapper  Source
Small Gray Snapper Source
Gray Snapper  Source 
Gray Snappers near sea rod soft corals
Gray Snapper  Source 
Gray Snapper  Source 
Gray Snapper have large jaws on a pointed snout.  The outer pair of canine teeth in the upper jaw is much larger than those in lower jaw.  Gray Snapper are most similar to the Cubera Snapper Lutjanus cyanopterus, except the tooth patch on the roof of the mouth (called vomerine tooth patch) is V-shaped with an extension, resembling an arrow, whereas the tooth patch of the Cubera Snapper is simply V-shaped.  Be careful, you have to navigate past those canine teeth to get a look. 
Close up of the jaw teeth of Gray Snapper.  Photo by Chris G. Miller  source  
Small fish around 2 to 3 inches (5-7 cm) are very common in low salinity waters and range much farther into low-salinity estuaries than any other snapper species.  In fact, they have been captured in some lakes in Florida.  Small Gray Snapper are typical visitors to the lower Chesapeake Bay during summer and fall.   Young Gray Snapper are distributed in shallower water and are common on grass flats, among mangroves, and in other estuaries. They retain the wavy blue lines on their faces until they are 10 to 11 inches long (25-27 cm) —the entire time that they live inshore in bays. At that size they are willing feeders, and will quickly take a baited hook.  Larger fish are found in deeper water, both nearshore and offshore. 

Gray Snapper display an opportunistic feeding strategy, referred to as euryphagic carnivores.  They feed on crustaceans, such as shrimp and crabs,  and to a lesser degree on worms and mollusks,  but will also eat smaller fish. Juveniles feed diurnally and feed primarily on penaeid shrimp and crabs.  Larger fish also eat  cephalopods and become increasingly piscivorous, feeding more on fishes such as grunts (Haemulidae), if available. 
Distribution of the Gray Snapper.  Source:  IUCN.org
In Virginia waters the maximum size of adults is 18-24 inches. However, in more subtropical and tropical latitudes and offshore waters they may attain a larger size.  Typical size of the catch in shallow, inshore waters is between 8 and 14 inches. Gray Snapper is the most sought after recreational fish in southwest Florida.   They are easy to catch on shrimp or cut bait and are often caught near structures like wrecks, bridges, and docks. The minimum size is 10 inches in state waters and in federal waters (from 9-200 nautical miles) the minimum size limit is 12 inches.  The oldest Gray Snapper observed in Florida waters was 25 years.   The IGFA records of 17 pounds has stood since 1992. 
Twelve pound Gray Snapper.  Source 
Although the Gray Snapper is distributed from the mid-Atlantic south to Brazil, they may be one of the most common food fish in parts of the Caribbean where they occur in large aggregations. They migrate offshore to spawn in summer months. During the full moon, numerous Gray Snapper exhibit the spawning rush, where they swim up in the water column releasing large clouds of gametes. There is no courtship or mate selection nonsense, rather it is group sex worthy of the "Shades of Gray Snapper" blog title.  Watch the video.   The fertilized eggs develop and hatch within a day and the larvae remain planktonic for 20 to 33 days as they develop (Allman and Grimes 2002).  Gray Snapper juveniles settle into shallow seagrass beds where they grow for 8 to 10 months and expand their home range and reach a size of about 10 to 12 cm.  Here they are likely to colonize mangrove shoreline habitats (Faunce and Serafy 2007).  Some postulate that the shallow nearshore environments serve as “waiting room” habitats to allow the reef fishes to grow and avoid intense predation pressure before colonizing adjacent reef habitats (Grol et al. 2011).  Consequently, the mangroves may be important secondary or sequential habitat for supporting large populations of the Gray Snapper.     
Mean size of Gray Snapper increases with distance from inlet presumable due to exclusion of small fish. Hashed area is size of Gray Snapper in sea grass beds.  From Faunce and Serafy (2007)
Using acoustic tagging, Luo et al. (2009) revealed that Gray Snappers display a distinct diel migration pattern, whereby shallow seagrass beds are frequented at night and mangroves and other complex habitats were frequented during the day.  This pattern may maximize growth and minimize predation risk.  Survivors eventually obtain large size and move from shallows to bay to ocean reefs. 
Juvenile Gray Snapper associate with Sea Grass beds (Turtle Grass Thalassia testudinum). Photo from San Salvador Island, Bahamas.  Source  
The ontogenetic and diel movements of the Gray Snapper provide direct support for the strategy of conserving both inshore seagrass and mangrove habitats as well as offshore coral reefs.  Gray Snapper are also at risk from harvest in shrimp trawls. The juvenile Gray Snapper often overlaps in soft-bottom habitats that support abundant shrimp populations.   Consequently, shrimp trawlers account for a large portion of the fishing mortality of Gray Snapper.  Gray Snapper are also harvested as bycatch in commercial fisheries for Red Snapper. 

No-take sanctuaries are one strategy for protecting exploited populations, critical habitats, community structure, and corals.   Gray Snapper in one no-take zone in Florida were larger than other waters (Faunce et al. 2002). No-take zones enhance the abundance of another highly valuable snapper (Malcolm et al. 2015); perhaps it is time to expand the application of the strategy.

Gray Snapper is a common component of coral reef ecosystems, which are among the most diverse, albeit frequently altered, marine ecosystems.  Coral reefs are not limited by solar energy, but by nutrients stored and cycled by living organisms.  Consequently, the Gray Snapper must be a key processor and recycler of nutrients because their biomass is high and they annually recruit new individuals to the reef.  In a recent study, Allgeier et al. (2016) demonstrated that fishing reduced fish-mediated nutrient processes by nearly half. Coral reef fish, such as the Gray Snapper, slowly and steadily feed (via concentrated urine) the coral reef ecosystems that, in turn, provide food and shelter to the fish. Selective fishing removes the nutrient pool and the fertilization effect. In the Florida Keys and presumably elsewhere, Gray Snapper are often overfished (Ault et al. 1997).  The recovery and restoration of damaged coral reefs is a long term prospect that depends on protecting the coral reef fishes, such as the Gray Snapper, in addition to protecting the coral reefs. Time for fish biomass to return to equilibrium levels after fishing has ended can take 25 years (McClanahan et al. 2016).  Protect large fishes, such as grouper, snapper or barracuda, and you protect the storage and slow release of nutrients. Gray Snapper and their pee provide ecosystem services that sustain healthy coral reefs. 
Gray Snapper. Photo by Ned DeLoach  Source 
Allgeier, J.E., A. Valdivia, C. Cox, and C.A. Layman. 2016. Fishing down nutrients on coral reefs.  Nature Communications DOI: 10.1038/ncomms12461
Allman, R.J., and C.B. Grimes. 2002.  Temporal and spatial dynamics of spawning, settlement, and growth of gray snapper (Lutjanus griseus) from the West Florida shelf as determined from otolith microstructures. Fisheries Bulletin 100:391-401.
Ault, J.S., J.A. Bohnsack, and G.A. Meester.  1997. A retrospective (1979-1996) multispecies assessment of coral reef fish stocks in the Florida Keys.  Fishery Bulletin 96:395-414.
Faunce, C.H., J.J. Lorenz, J.A. Ley, J.E. Serafy. 2002.  Size structure of gray snapper (Lutjanus griseus) within a mangrove 'no-take' sanctuary. Bulletin of Marine Science 70:211-216.
Faunce, C.H., and J.E. Serafy.  2007.  Nearshore habitat use by Gray Snapper (Lutjanus griseus) and Bluestriped Grunt (Haemulon sciurus): environmental gradients and ontogenetic shifts.  Bulletin of Marine Science 80:473-495.
Florida Fish and Wildlife Conservation Commission.  2014.  Species Account Gray Snapper, Lutjanus griseus (Linnaeus, 1758).  Website.  http://myfwc.com/research/saltwater/status-trends/finfish/gray-snapper/ Accessed January 24, 2016.
Grol, M.G.G., I. Nagelkeken, A.L. Rypel,  C.A. Layman. 2011. Simple ecological trade-offs give rise to emergent cross-ecosystem distributions of a coral reef fish.  Oecologia 165:79-88.
Malcolm, H.A., A.L. Schultz, P. Sachs, N. Johnstone, and A. Jordan. 2015.  Decadal changes in the abundance and length of snapper (Chrysophrys auratus) in subtropical marine sanctuaries. PLOS One       http://dx.doi.org/10.1371/journal.pone.0127616.
McClanahan T.R., J.M.Maina, N.A.J. Graham, and K.R Jones.  2016. Modeling reef fish biomass, recovery potential, and management priorities in the western Indian Ocean. PLOS ONE 11(6): e0156920. doi: 10.1371/journal.pone.0156920

Friday, January 20, 2017

Sea Lamprey and Unexpected Costs of Shipping, by Don Orth

Among the many invasive fishes, one of the best-studied invasive fish is the parasitic Sea Lamprey (Petromyzon marinus).  Sea Lamprey is the subject of many vertebrate anatomy labs because they represent a morphologically simple fish.  The Sea Lamprey skeleton is cartilaginous, and they lack jaws, scales, and paired fins.  Sea Lamprey have two closely spaced dorsal fins, functional eyes, and seven gill openings.  The mouth of this blood-sucking parasite is most unique.  Sea Lamprey have a circular oral disc with circular rows of sharp, curved teeth and file-like tongue.  After latching on to a large-bodied fish, the Sea Lamprey uses its teeth to rasp through the skin and feed on the blood. The host may die directly from loss of fluids or indirectly from infections of the wound.  If the host fish survives, it may be attacked again by another feeding Sea Lamprey. The Sea Lamprey is an anadromous species native to the North Atlantic Ocean; they breed in rivers in Europe and North America from Newfoundland to Florida.  Sea Lamprey are in the order, Petromyzontiformes, which encompasses forty known species of lampreys worldwide. However, landlocked populations in the Great Lakes have gotten most attention by scientists and anglers, who have crafted the narrative of invader to control at all costs.
Sea lamprey adult. Photo by Oskar Sindri Gislason
Sea Lamprey were a major, or final, cause of the collapse of major commercial fisheries for Lake Trout Salvelinus namaycush, several Whitefishes Coregonus spp., Burbot Lota lota, and Walleye Sander vitreus in the 1940s and 1950s.  Because the Sea Lamprey reduced populations of these large piscivorous fishes, the next invasive fish to arrive, the Alewife Alosa pseudoharengus, quickly become the dominant prey fish in Lakes Ontario, Huron, and Michigan.  The expansion of the Alewife led to introduction of trout and salmonine fishes in 1968 and creation of new multi-million dollar recreational fisheries.  That management controversy is a subject for another essay (Kitchell and Sass 2008; O’Gorman et al. 2013). 
Sea Lamprey oral disc. Photo by Cory Genovese
Expensive and persistent control efforts to reduce abundance of Sea Lamprey began in Lake Superior and spread eastward so that lamprey control in Lake Ontario began in 1971 and suppression was not evident until 1988.  Current control relies primarily on stream application of two lampricides, 3-trifluoromethyl-4-nitrophenol (don't you love organic chemistry now?), or more simply TFM, and Bayluscide.  TFM and Bayluscide are applied to kill larval Sea Lampreys before they metamorphose and emigrate from spawning streams.  Other control techniques include harvest of adults via trapping, and low-head barriers built to reduce the amount of stream habitats that need to be treated with TFM. For more background, view this video Silent Invaders.   Along with effective Sea Lamprey control efforts, harvest controls, stocking, and restoration have also increased abundance of large-bodied fishes, which are hosts for Sea Lamprey. If they did not have such large economic effects, basic questions on the species would not have been addressed.  Consequently, we know a lot about the Sea Lamprey, certainly more than any other lamprey in the world.
The conventional wisdom always held that the Sea Lampreys first entered the Great Lakes in the 1800s through the man-made locks and shipping canals around Niagara Falls.  Niagara Falls was a natural barrier to Sea Lamprey migration above Lake Ontario.  Completion of Erie Canal provided access to from the Hudson River to Lake Erie. Modification of Welland Canal in 1919 provided access between Lake Ontario and Lake Erie. Consequently, Sea Lamprey first appeared in Lake Erie in 1921, and subsequently were documented in Lake Michigan (1936), Lake Huron (1937), and Lake Superior (1946). But what about the status of Sea Lampreys in Lake Ontario?  Recent DNA analyses supports hypothesis that Sea Lamprey are indigenous to Lake Ontario and introduced in other Great Lakes (Waldman et al. 2004, 2006). Unique alleles found in Lake Ontario, but absent in the Atlantic coast collections, would have taken many thousands of years to develop (Waldman et al. 2009).  It is likely that the populations of Sea Lamprey in Lake Ontario and its tributaries, the Finger Lakes, and Lake Champlain once represented relict populations from the last Pleistocene glaciation.  

Erie Canal (Top) source  and Welland Canal (bottom) source
Because of the emergence of the Sea Lamprey and their economic impacts in the upper Great Lakes, much has been learned about the Sea Lamprey.   How they locate their spawning grounds?  How do they locate mates?   The key is chemical, or pheromone-based communication.    Larvae, or ammocetes, and adult males produce and release unique bile acids.  Adults have a small nasal opening at the top of the head and can detect these bile acids at picomolar concentrations (Li et al. 1995; Li et al. 2002).   These finding led to the hypothesis that the bile acid compounds serve as pheromones.   Controlled behavioral tests supported the hypothesis that the pheromones released by larvae and transported downstream and serve to direct the migration of adults females (Bjerselius et al. 2000; Sorensen and Vreize 2003; Sorensen and Stacy 2004).  This research supports the evolutionary role that pheromones have played as chemical cues to the suitability of spawning and rearing habitat for the Sea Lamprey. This research also paved the way to consider another approach to Sea Lamprey control.  Migratory Sea Lamprey rely heavily on olfactory cues to locate river mouths and direct their upstream movement within rivers (Vrieze et al. 2010).   Pheromones could be used to divert migratory Sea Lamprey to tributaries where they may be trapped, poisoned, or sterilized.  Note the large olfactory bulbs in the lamprey brain image below.  
Sea lamprey brain after R.H. Burne
 Many anadromous fishes use olfactory cues to return to their natal home for spawning. Fish, such as Atlantic Sturgeon, Atlantic Salmon and Striped Bass, show significant differences in haplotype frequencies among rivers.  However, the Sea Lamprey do not return to their natal streams for spawning.  As parasites, the tendency for a regular migration circuit and return to a home river is problematic as their host fishes may disperse the parasite widely.   When adults reach maturity they quit feeding and need to find a suitable river for breeding.    Waldman et al. (2008) collected fin clips from Sea Lamprey from eleven Atlantic Slope rivers.  Examination of haplotype frequencies from mitochondrial DNA confirmed a very low variation among river collection sites. Therefore, the Sea Lamprey regularly inter-breed among rivers and demonstrate a regional panmixia and not homing (Waldman et al. 2008).    

With this knowledge, can we control the invasive Sea Lamprey more effectively?  In theory, yes.   Trapping alone in the absence of lampricides is not sufficient to control Sea Lamprey populations (Holbrook et al. 2016).  However, research is underway now to evaluate strategies to integrate multiple control strategies.   One technique releases large numbers of sterile males in an attempt to thwart successful reproduction.  These sterile males still produce sperm, but that sperm is genetically damaged, thereby reducing the number of viable embryos via lethal mutations.  Sterile release strategies, first tested in the early 1990s in the St Mary’s River, reduced survival of embryos in nests by half (Bravener and Twohey 2016). The graph below supports the significant effect that proportion of sterile males observed on nests had on the mean embryo viability of all nests.
Plot of embryo viability and proportion of sterile males on nests (Bravener and Twohey 2016).
The solid line represents the theoretical relationship under a baseline embryo viability of 43.4%. The dashed line represents the line of best fit to the 14 data points.
Another technique uses pheromones to disrupt migrations or attract spawners to areas where sterile males are released and/or where spawning adults may be more effectively trapped.  The pheromone compound can now be synthesized, which makes the technique operational.  The pheromone compound is 7α, 12α, 24-trihydroxy-3-one-5α-cholan-24-sulfate (don’t you love organic chemistry?), or more simply 3k PZS (Li et al. 2012).  Costs to synthesize 3k PZS have decreased substantially in the last ten years (Johnson et al. 2013). Dawson et al. (2016) evaluated strategies for pheromone-baited trapping by calculated expected control and their costs.   The findings support combining lampricides and pheromone-baited trapping technologies at comparable costs.  
 Sea Lamprey wound on Steelhead.    Photo by Boris Kitevski source
While the basic research on the Sea Lamprey has great potential to make control efforts more cost effective, costs will continue into the future.  The current management strategy for some Great Lakes fisheries depends on a strategy of stocking piscivores to drive down populations of the invasive Alewife and Rainbow Smelt and thereby reduce competition and predation effects of these invaders.  This strategy works, however, the net effect is more large-bodied fishes that serve as hosts for the parasitic Sea Lamprey.   Stocking piscivores provides more food for Sea Lamprey and leads to competition among salmon, lake trout, and burbot.  In addition, other invasives, including Zebra Mussel, Quagga mussels, Round Goby, and Tubenose Goby will most certainly complicate the future of Great Lakes fisheries.    There is no simple solution to living with invasive fishes.   In closing, remember that where you stand regarding the Sea Lamprey depends on where you sit.  The Sea Lamprey in its native range do not drive down abundance of large bodied fishes. Rather than a scourge, they play important roles.  In tributaries they are ecosystem engineers, creating patches of deep, rocky, and swift water next to deep, slow, and sandy habitat patches, as well as higher density of benthic invertebrates (Hogg et al. 2014).  

Bjerselius, R., and eight coauthors. 2000.  Direct behavioral evidence that unique bile acids released by larval sea lamprey (Petromyzon marinus) function as a migratory pheromone.  Canadian Journal of Fisheries and Aquatic Sciences 57:557-569.
Bravener, G., and M. Twohey. 2016. Evaluation of a sterile-male release technique: A case study of invasive Sea Lamprey control in a tributary of the Laurentian Great Lakes. North American Journal of Fisheries Management 36:1125-1138.
Dawson, H.A., M.L. Jones, B.J. Irwin, N.S. Johnson, M.C. Wagner, and M.D. Szymanski. 2016. Management strategy evaluation of pheromone-baited trapping techniques to improve management of invasive sea lamprey.  Natural Resource Modeling 29:448-469.
Hogg, R.S., S.M. Coghlan, Jr., J. Zydlewski, and K.S. Simon.  2014.  Anadromous sea lampreys (Petromyzon marinus) are ecosystem engineers in a spawning tributary.  Freshwater Biology 59:1294-1307.
Holbrook, C.M., R.A. Bergstedt, J. Barber, G.A. Bravener, M.L. Jones, and C.C. Krueger.  2016.  Evaluating harvest-based control of invasive fish with telemetry: performance of sea lamprey traps in the Great Lakes.  Ecological Applications 26:1595-1609.
Johnson, N.S. M.J. Siefkes, C.M. Wagner, H.A. Dawson, H. Wang, T.B. Steeves, M. Twohey, and W. Li. 2013. A synthesized mating pheromone component increases adult sea lamprey (Petromyzon marinus) trap capture in management scenarios.  Canadian Journal of Fisheries and Aquatic Sciences 70:1101-1108.    
Kitchell, J. F., and G. G. Sass. 2008. Great Lakes ecosystems: Invasions, food web dynamics and the challenge of ecological restoration. Pages 157–170 in D. Waller and T. Rooney, editors. Ecological history of Wisconsin. University of Chicago Press, Chicago, Illinois, USA.
Li., W., P.W. Sorensen, and D.G. Gallaher. 1995. The olfactory system of the migratory sea lamprey (Petromyzon marinus) is specifically and acutely sensitive to unique bile acids released by conspecific larvae. Journal of General Physiology 105:569-587.
Li, W., A.P. Scott., M.J. Siefkes, H. Yan, Q. Liu., S.-S. Yun, and D.A. Gage. 2002.  Bile acid secreted by male sea lamprey that acts as a sex pheromone.  Science 296:138-141. 
Li, K., M.J. Siefkes, C.O.Brant, and W. Li. 2012. Isolation and identification of petromyzestrosterol, a polyhydroxysteroid from sexually mature male sea lamprey (Petromyzon marinus L.). Steroids 77:806-810.
O’Gorman, R., C.P. Madenjian, E.F. Roseman, A.Cook, and O.T. Gorman. 2013. Alewife in the Great Lakes: Old invader – New millennium    Pages 705-732 in W.W. Taylor, A. J. Lynch, and N. J. Leonard editors. Great Lakes Policy and Management: A Binational Perspective, 2nd edition. Michigan State University Press, East Lansing
Sorensen, P.W., and L.A. Vrieze. 2003. The chemical ecology and potential application of the Sea Lamprey migratory pheromone. Journal of Great Lakes Research 29(Supp 1):66-84.
Sorensen, P.W., and N.E. Stacey. 2004.  Brief review of fish pheromones and discussion of their possible uses in the control of non-indigenous teleost fishes.  New Zealand Journal of Marine and Freshwater Research 38:399-417.
Vrieze, L.A., R. Bjerselius, and P.W. Sorensen. 2010.  Importance of the olfactory sense to migratory sea lampreys Petromyzon marinus seeking riverine spawning habitat. Journal of Fish Biology 76:949-964.     
Waldman, J.R., C. Grunwald, N.K. Roy, and I.I. Wirgin. 2004. Mitochondrial DNA analysis indicates sea lampreys are indigenous to Lake Ontario. Transactions of the American Fisheries Society 133:950-960. 
Waldman, J.R., C. Grunwald, and I.I. Wirgin. 2006. Evaluation of the native status of sea lamprey Petromyzon marinus in Lake Champlain based on mitochondrial DNA sequencing analysis. Transactions of the American Fisheries Society 135:1076-1085.
Waldman, J., R. Daniels, M. Hickerson, and I. Wirgin. 2009. Mitochondrial DNA analysis indicates sea lampreys are indigenous to Lake Ontario: response to comment. Transactions of the American Fisheries Society 138: 1190-1197.