Climate Change and The Fishes, by Don Orth

F. Sherwood Rowland was an atmospheric scientist who studied inert gases, namely chlorofluorocarbons (CFCs), widely used as refrigerants and aerosol propellants. In a 1974 paper in Nature, he first recognized the threat that CFCs posed to the Earth’s ozone layer.  As the story goes, one evening he remarked to his wife, Joan, that the research “is going very well, but it may mean the end of the world.”  His research and associated “fear and doom” led to global environmental action to eliminate CFCs, which were eventually banned. Rowland’s research saved the planet; it did not mean the end of the world.   

Today, most atmospheric scientists accept the reality of global climate change and each year new records are set (Feltman 2017).  Yet, many atmospheric scientists who study global climate are criticized for framing the climate change with language that connotes fear and doom. Researchers Michael Mann and Lee Kump, in Dire Predictions: Understanding Climate Change, present the evidence to support the contention that climate change is real, caused by human activities, and is already a threat. There is no longer any excuse for delaying a shift away from fossil fuel energy.  The research is based on basic principles of physics and chemistry that allow us to predict that the Earth will warm as concentrations of greenhouse gases increase.  Of course, Mann and Kump have been criticized for creating alarmism in the climate sciences. 

 

Number of years per decade that had above-average temperatures—and how many of those years rose a half, or even a whole, degree above the norm (Feltman 2017). 

We do not know how fishes will adapt to a warmer earth. The science involves physics and chemistry of aquatic ecosystems as well as many other fields of inquiry.  Those who fish have already observed changes in their catches as warm-water fish are increasing observed in northern latitudes or high elevation waters.  Managing fish in a warming world will prove to be extremely complicated as fish re-distribute or adapt to the changing conditions.  

Some changes are already evident.  For example, Neala Kendall, Gary Marston, and Matthew Klungle, from the Washington Department of Fish and Wildlife, reported on the decline in ocean survival and abundance of Steelhead Trout (anadromous Oncorhynchus mykiss), raising concerns about long-term viability of stocks in the Puget Sound and south.  However, over the study period, temperature does not have a simple relationship to smolt survival.  This region has also undergone an ecosystem shift of the past several decades leading to demersal fish declines and increases in harbor seal Phoca vitulina and harbor porpoises Phocoena phocoena (both smolt predators).  Consequently, forecasting future changes will be highly uncertain depending on behavior of multiple predators. 

Perhaps fish in other smaller, inland systems will be easier to understand. In Michigan, streams with higher relative groundwater inputs are less sensitive to temperature changes and, therefore, more suitable for Brook Trout (Salvelinus fontinalis), Brown Trout (Salmo trutta), and Rainbow Trout (Oncorhynchus mykiss) (Carlson et al. 2017).   Observed stream temperatures in Shenandoah National Park were also less sensitive to air temperature due to the moderating effect of shallow groundwater inputs (Snyder et al. 2015). Consequently, these coldwater thermal refugia will become even more important in the future. Policymakers and stakeholders should map and protect these habitats to conserve salmonid populations as the climate warms. Moreover, this management action is correct no matter whether the water temperature increases 2 or 4 °C in the next 50 years.  Perhaps, the action can be generalizable to other regions (Isaak et al. 2015; Myers et al. 2017).    

However, much of the research to date assumes the species traits and other aspects of aquatic communities do not change.  Novel research to explore shifts in species traits (Ayllón et al. 2016) is necessary to realistically evaluate long-term changes in response to climate change. Evidence of evolutionary responses to climate change is limited to observations of shifts in timing of migration and spawning. 

Species distribution model predictions of probability of occurrence for the Kanawha Minnow Phenacobius teretulus and Appalachia Darter Percina gymnocephala in the New River drainage (Huang et al. 2016).  

Freshwater fishes face losses due to many factors in addition to climate change. Habitat loss, fragmentation of habitat, pollution, hydrologic alteration, invasive species, and overexploitation are pervasive issues.  Compared to salmonids, relatively little work has been done to assess the risk of climate change on other freshwater fishes. Species distribution models have been applied to fishes in the United States. Because the distributions are very sensitive to climate and land use, they may prove useful to projecting new distributional patterns given an altered climate (Bouska et al. 2015; Huang et al. 2016). In southern Appalachia, many cold and coolwater fishes on private lands are most at risk for local extirpations.  The species distribution models for two coolwater endemic fishes, Kanawha Minnow Phenacobius teretulus and Appalachia Darter Percina gymnocephala, demonstrate the importance of remaining coolwater fragments that support the only surviving populations of these species.  Similarly, some rare headwater fishes, such as the Clinch Dace (Chrosomus sp. cf. saylori), have no other cool places to move when temperatures rise.   

Clinch Dace is a headwater specialist with very limited distribution in Virginia. Photo: D.J. Orth

The Smallmouth Bass Micropterus dolomieu is a popular game species whose distribution will shift northward as thermal regimes warm.   However, the Smallmouth Bass may contract in the southern extent of its range where groundwater refugia are lacking.   In the southern parts of the range, growth is slow and summer growth may be limited by climate (Brewer 2013).   

Seasonal growth curve for Smallmouth Bass from a stream at the southern edge of the native range.  Median length at age is typically 20% longer. (Orth et al. 1983).

Pease and Paukert (2013) predicted that by 2060, the growth potential of Smallmouth Bass would increase by 3–17% due to stream warming, if not limited by food availability.  So it’s not enough to study Smallmouth Bass in isolation of its food sources.  Moreover, each stream occupied by Smallmouth Bass is different, some in very important ways.  Middaugh et al. (2016) examined potential differences in stream temperature across flow regimes as some stream will change more than others with climate change. We also cannot assume that fish won’t move.  Westoff et al. (2016) discovered that migratory behavior allowed the Smallmouth Bass to thermoregulate. Streams with large springs can moderate water temperatures in the stream during the warmest part of the year, creating thermal refugia (Westoff and Paukert 2014).  
 

Lynch et al. (2016) reviewed 31 studies that documented fish responses to climate change in inland waters of North America.  Most have dealt with the valuable stocks of Pacific salmon.  In Ontario lakes Smallmouth Bass may demonstrate enhanced recruitment, survival, and dispersal with warming temperatures.  In the arid southwest, climate change changes flow, thereby influencing reproductive phenology of fishes and reducing river-floodplain connectivity.  In the diverse streams of southeastern US, the interaction of climate change and pervasive anthropogenic influences makes it difficult to separate the interacting causes.   However, many stenothermic fishes are replaced by more eurythermic fishes. Lynch et al. (2016) make a number of recommendations for future research.  Importantly, they highlight the importance of identifying processes that buffer fishes from climate change, such as groundwater upwelling, phenotypic plasticity, and adaptive microevolution.  Research on resilience is lacking. 

Documented responses of fishes in the southeastern USA to climate change. Green arrows indicate an increase or earlier seasonal response, and gray arrows indicate a decrease or later seasonal response  (Lynch et al. 2016).

We all feel somewhat helpless in dealing with an issue as pervasive as climate change. There are really only three options: Mitigate, Adapt, or Suffer. Only humans are able to take action to mitigate for effects of greenhouse gas emissions.  If we fail to act, we must adapt. If we cannot adapt we will suffer.  When dealing with fishes, much uncertainty is to be expected as we attempt to save the fishes. We’re not sure all the ways in which fish may adapt.  However, projections of continued warming through mid-century means that extirpations of some populations will be inevitable and salmonids in particular are undergoing a global decline (Isaak et al. 2015). While the options in the Rocky Mountains include more public lands, that is not the case elsewhere.  I know, I am making dire predictions (= fear and doom).  So be it. Many stakeholders will need to be rallied to enable protection of climate refugia to ensure conservation of many cool and coldwater fishes.  Only time will tell.  Will the future climate lead to adaptations that allow fish to thrive,  or will we see inaction that leads to losses of freshwater biodiversity.
 

References

Ayllón, D., S.F. Railsback, S. Vincenzi, and V. Grimm. 2016.  InSTREAM-Gen: Modelling eco-evolutionary dynamics of trout populations under anthropogenic environmental change. Ecological Modelling 326: 36-43.

Bouska, K.L., G.W. Whitledge, and C. Lant. 2015. Development and evaluation of species distribution models for fourteen native central U.S. fish species. Hydrobiologia 747: 159. doi:10.1007/s10750-014-2134-8

Brewer, S.K. 2013. Groundwater influences on the distribution and abundance of riverine Smallmouth Bass, Micropterus dolomieu, in pasture landscapes in the midwestern USA. River Research and Applications 29:269-278.

Carlson, A.K., W.W. Taylor, K.M. Schlee, T.G. Zorn, and D.M. Infante. 2015. Projected impacts of climate change on stream salmonids with implications for resilience-based management Ecology of Freshwater fish 26:190-204.  

Feltman, R. 2017.  Don’t believe our planet is warming up?  Look at this.  Popular Science. July-August.  Accessed July 13, 2017, at http://www.popsci.com/climate-change-infographic-our-warming-planet

Huang, J., E.A. Frimpong, and D.J. Orth. 2016. Temporal transferability of stream fish distribution models: can uncalibrated SDMs predict distribution shifts over time? Diversity and Distributions 22:651-662.

Isaak, D.J., M.K. Young, D. E. Nagel, D. L. Horan, and M.C. Groce. 2015. The cold-water climate shield: delineating refugia for preserving salmonid fishes through the 21st century. Global Change Biology   21:2540-2553.  

Lynch, A.J., B. J. E. Myers, C. Chu, L.A. Eby, J. A. Falke, R. P. Kovach, T.J. Krabbenhoft, T.J. Kwak, J. Lyons, C.P. Paukert, and J.E. Whitney. 2016. Climate change effects on North American inland fish populations and assemblages, Fisheries, 41(7):346-361.

Middaugh, C.R., B. Kessinger, and D.D. Magoulick. 2016. Climate-induced seasonal changes in smallmouth bass growth rate potential at the southern range extent. Ecology of Freshwater Fish DOI: 10.1111/eff.12320

Myers, B.J.E., C.A. Dolloff, J.R. Webster, K.H. Nislow, B. Fair, and A.L. Rypel. 2017. Fish assemblage production estimates in Appalachian streams across a latitudinal and temperature gradient.  Ecology of Freshwater Fish  DOI: 10.1111/eff.12352

Orth, D.J., D.D. Oakey, and O.E. Maughan. 1983. Population characteristics of smallmouth bass in Glover Creek, southeast Oklahoma.  Proceedings of the Oklahoma Academy of Science 63:37-41.

Pease, A.A., and C.P. Paukert. 2013. Potential impacts of climate change on growth and prey consumption of stream-dwelling smallmouth bass in the central United States. Ecology of Freshwater Fish 23:336-346.

Lessons from Lionfish, by Don Orth

Invasions are scary and often lead to a simple logic. Invasive species are bad.  The Lionfish is an invasive species. Therefore, we should kill and remove all lionfish.  While some people support categorization of species as invasive based solely on its origin, others seek for evidence of economic or environmental harm or harm to human health. There is much in the news about the Lionfish invasion, and here I highlight some of the latest findings on the lionfish, how we can discuss the controversy with students, and speculate on what comes next.  

Red Lionfish Pterois volitans   Photo by D.J. Orth

Lionfish (Pterois) are a fish in the Scorpaenidae family. They are are native to the Indo-Pacific ocean.  There are many species characterized by large, venomous spiky fin rays and warning coloration and banding patterns.  Two species are recent invaders in the western Atlantic, Gulf of Mexico, and Caribbean Sea, the Devil Firefish (Pterois miles) and the Red Lionfish (P. volitans).  Lionfish were first introduced to south Florida in the mid-1980’s and became established and common within ten years (Schofield 2009).  This was the first non-native marine fish to become established in the western Atlantic.  Invasion and spread were imminent, but there were no plans in place to deal with potential effects.  The combination of generalist feeding stratey, cryptic coloration, and undetectable chemical cues made the lionfish particularly successful in colonizing reefs where large predators were overfished.  Lionfish quickly rose to high densities and ate many small fish and invertebrate species (Côté et al. 2013).   

While considering these characteristics and early studies in small patch reefs in the Bahamas, scientists proposed a “worst case scenario in which most reef-fish biomass was converted to lionfish biomass, leaving invaded reefs depauperate of native fishes” (Albins & Hixon 2011; Albins 2015).  Emergence of the lionfish stimulated coordinated and long-term study by numerous investigators. The lionfish appeared in The Bahamas in 2004 and Green et al. (2012) observed a decline in 42 prey fishes during a rapid increase in lionfish abundance. Lionfish  reduced the abundance of many fishes, such as the Tomtate (a native forage fish Haemulon aurolireatum), as much as 45% since the invasion began in the hard-bottom reef habitat in Atlantic waters from North Carolina to Florida (Bellew et al. 2016).

Tomtate Haemulon aurolireatum is one of many prey species of the lionfish.   Illustration: © Diane Rome Peebles    

(Left) Standardized Tomtate abundance per trap at different stages of the lionfish invasion for areas not invaded by lionfish (gray points) and areas invaded by lionfish (red points). (right) Lionfish-attributed change in tomtit abundance.  Bellew et al. (2016).

But among the reefs along the coast of Belize, lionfish had no apparent effect on native prey communities four years post-invasion.  Oops!  Unexpected finding not concordant with prevailing storyline!   Serena Hackerott and her colleagues quantified lionfish and the density, richness, and composition of native prey fishes at sixteen reefs along of the Belize Barrier Reef from 2009 to 2013. Using a powerful, before-after-control-impact study design with reefs that spanned approximately 250 kilometers, they detected no evidence that lionfish measurably influenced the density, richness, or composition of prey fishes.  Similar findings were reported by Elise et al. (2015) from the Archipelago Los Roques National Park, Venezuela.

Source 

Why?  habitat complexity had up to five times greater effect on the density and richness of some families of small reef fishes than lionfish densities.  Of course, the lionfish did eat many small reef fishes. Disparate findings are largely dependent on the spatial and temporal scale of experiments.  In experiments that demonstrated a significant effect on reef fish recruits, lionfish comprised 50–100% of the predator biomass (Albins & Hixon 2011; Albins, 2015), whereas in the Belize reef study lionfish were only 10% of the total potential predator biomass.  Perhaps a longer study is needed? Perhaps lionfish are less likely to have apparent impacts in more intact protected reef ecosystems, such as the Belizean Barrier Reef. 

What are the options besides doing nothing? First, there is the invasivorism solution, where we “Eat our way out” of the lionfish problem and create a market-based solution for this dangerous and delicious fish (Chapman et al. 2016).  Second, manage large top predators, such as groupers, to eat the lionfish.  Third, annihilate all the lionfish with robots.  Fourth, discover some novel lionfish control methods.  The "Eat our way out" solution was hindered when the FDA announced a significant risk from ciguatera poisoning and  recommended that lionfish from certain areas not be eaten (Robertson et al. 2013). 

Plot of lion fish biomass versus grouper biomass at 71 reef sites (Valdivia et al. 2014). Black dots=protected sites, grey dots=non-protected sites, and red squares=sites from Mumby et al. (2011). 

The Bahamas is home to the oldest MPA in the world, the Exuma Cays Land and Sea Park, created in the 1950s, and a 20-year fishing ban here enabled grouper populations to recover from overfishing. Mumby et al. (2011) discovered a negative correlation (see red line and data in figure) between lionfish and grouper biomass,  suggesting that large grouper may serve as a natural biocontrol in no-fishing areas. However, in a follow-up study, Valdivia et al. (2014) concluded that we cannot rely on current native grouper populations to control the lionfish.  Manual removals appear to be effective at least at short timeframes in small areas (Bellew et al. 2016).  However, because the lionfish are more abundant in deeper, edge-of-sea locations, complete control is unlikely at larger spatial scales. How will the lionfish respond to robot predators? Côté et al. (2014) learned that the lion fish responded to culling by lowering their activity levels and hiding more. 

Robotic lionfish zapper.  Photo by J-P ROUJA/LOOKBERMUDA

Is the worst-case scenario happening? Studies by numerous investigators support no effect to varying degrees of negative effect.  It appears that negative effects are more typical in small scale, isolated reefs while effects on large open systems is less certain.   The scientific consensus is far from settled and most research has focused on effects on the reef fish with far less attention paid trying to understand stakeholders’ views on this species and its management.   

Caballo-Cárdenas (2017) claims that the dominant discourse labels the lionfish as “ultimate predators” that are a threat and characterize control efforts as a war.  Lionfish hunting and consumption by humans are deemed a necessary part of the war effort.  In presenting this case to students, it is important to first compare the criteria for invasive species.  Should invasive species be categorized based simply on their origin?  Or should we define "invasive species" as a species that is: (1) non-native (or alien) to the ecosystem under consideration, and (2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.   Next, we may discuss what Moore (2012) means when she says that the lionfish and fishermen are malleable?   What roles do social scientists play in the management of introduced fishes, such as the lionfish?   How do fisheries emerge and become sustainable?  What evidence support the position that the lionfish is a 'keystone species' ?  After discussion of these issues, students may explore other examples of invasive species, the problems they caused and proposed solutions.

Many unanswered questions remain concerning this new addition to our marine reef ecosystem.  Will they learn to be more wary ?   What is the role of marine protected areas and should be remove lionfish from MPAs? (Cox et al. 2017).  What would happen if we restore populations of apex predators in reef environments? (Valdivia et al. 2014).   There are many more questions than answers.   No matter what new discoveries may occur,  the lionfish has changed the way that marine fish managers view invasive fish forever.

For more information click here. 

References

Albins, MA. 2015. Invasive Pacific lionfish Pterois volitans reduce abundance and species richness of native Bahamian coral-reef fishes. Marine Ecology Progress Series 522:231-243

Albins MA, and MA Hixon. 2011. Worst case scenario: potential long-term effects of invasive predatory lionfish (Pterois volitans) on Atlantic and Caribbean coral-reef communities. Environmental Biology of Fishes 96:1151-1157

Bellew, N.G., N.M. Bacheler, G.T. Kellison, and A.M. Schueller. 2016.  Invasive lionfish reduce native fish abundance on a regional scale. Scientific Reports 6: 32169   doi: 10.1038/srep32169.  

Caballo-Cárdenas, E.C. 2016. Controversies and consensus on the lionfish invasion in the Western Atlantic Ocean. Ecology and Society 20(3); 24. http://dx.doi.org/10.5751/ES-07726-200324

Chapman, J.K., L.G. Anderson, C.L.A. Gough, and A.R. Harris. 2016. Working up an appetite for lionfish: a market-based approach to manage the invasion of Pterois volitans in Belize. Marine Policy 73:256-262

​​Côté, I.M., S.J. Green, J.A. Morris, Jr., J.L. Akins, and D. Steinke D. 2013. Diet richness of invasive Indo-Pacific lionfish revealed by DNA barcoding. Marine Ecology Progress Series 472:249-256.

Côte, I.M. et al.  2014. What doesn’t kill you makes you wary? Effect of repeated culling on the behaviour of an invasive predator. PLOS One 9(4):    doi: 10.1371/journal.pone.0094248.

Cox, C.E., A. Valdivia, M.D. McField, K.D. Castillo, and J.F. Bruno. 2017. Establishment of marine protected areas alone does not restore coral reef communities in Belize. Marine Ecology Progress Series 563:65-79.

Elise, S., I. Urbina-Barreto, H. Boadas-Gil, M. Galindo-Vivas, and M. Kulbicki.   2015. No detectable effect of lionfish (Pterois volitans and P. miles) invasion on a healthy reef fish assemblage in Archipelago Los Roques National Park, Venezuela. Marine Biology 162(2): 319-330.

Green, S.J., J.L. Akins, A. Maljković, and I.M. Côté. 2012. Invasive lionfish drive Atlantic coral reef fish declines. PLOS One 7: e32596

Hackerott S, A. Valdivia, C.E. Cox, N.J. Silbiger, and J.F. Bruno. 2017. Invasive lionfish had no measurable effect on prey fish community structure across the Belizean Barrier Reef. PeerJ 5:e3270 https://doi.org/10.7717/peerj.3270

Moore, A. 2012.  The aquatic invader: Marine management figuring fishermen, fisheries, and lionfish in The Bahamas. Cultural Anthropology 27(4): 667–688.

Mumby, P.J., A.R. Harborne, and D.R. Brumbaugh. 2011. Grouper as a natural biocontrol of invasive lionfish. PLoS ONE 6(6): e21510. https://doi.org/10.1371/journal.pone.0021510.

Robertson, A. 2013. Invasive lionfish (Pterois volitans): a potential human health threat for ciguatera fish poisoning in tropical waters.  Marine Drugs 12(1): 88-97. 

Schofield, P. 2010. Update on geographic spread of invasive lionfishes (Pterois volitans [Linnaeus, 1758] and P. miles [Bennett, 1828]) in the Western North Atlantic Ocean, Caribbean Sea and Gulf of Mexico. Aquatic Invasions 5: S117-S122

Valdivia, A., J.F. Bruno, C.E. Cox, S. Hackerott, and S.J. Green. 2014. Re-examining the relationship between invasive lionfish and native grouper in the Caribbean. PeerJ 2:e348 http://dx.doi.org/10.7717/peerj.348