Mismanaged Fisheries: Don’t forget the invertebrates

When we think of fisheries, we usually think of, well, fish.  As the collective global negligence regarding fisheries is further studied and exposed, these resource management issues have been brought out of obscurity in the past decade or so.  Fisheries worldwide totaled 15-20 million metric tons (MMT) in the 1950s, rising to ~85 MMT by the 1990s.  However, this was a non-linear ascent.  Global catch increased from 6% per year in the 1950s and 1960s and declined to 2% through the 1980s, finally falling to zero in the 1990s—all the while with increasing fishing effort.  We are reaching (or have already reached) the maximum productivity potential for the global ocean.  Estimates have placed world overcapacity at around 30%:  a measure of how much more money has been invested in fishing capacity than can be returned due to the oversupply of vessels.  Ironically, this cycle of overinvestment and overfishing is not economically viable.  Humans are essentially fishing out the watery realms of Earth, fundamentally restructuring enormous ecosystems, and it’s not even cumulatively profitable.  The value of all of the fish caught worldwide is ~70 billion USD but conservatively, the global catch costs 91-116 billion USD to attain.  Although pointed out in the early 1990s, no real global action has been taken and mechanisms such as government subsidies are necessary to keep things afloat.   The northern Atlantic, once home to long-lived, piscivorous (eats fish) fishes is now dominated by shorter-lived, plankivorous species, reflecting the industry’s predilection for high trophic-level fishes.  Interesting, considering that 90% of energy is lost at each successive trophic level1.  Globally, the ocean has lost 90% of all large pelagic fishes according to a 2003 study2–a staggeringly downward trend that even some marine scientists have struggled to accept but has since been further confirmed in other works3.

In the face of such utter enormity of human-caused pressures within global fisheries, much less attention has been focused on invertebrates, particularly invertebrates collected for purposes other than food.  For example, there is much contemporary interest in developing pharmaceuticals from marine invertebrates.  This is not a new idea.  These organisms have been collected and used for medicinal purposes at least since the 5th century BCE, being especially widespread in the ancient Greek and Byzantine periods.  Inverts were used for digestive, skin, and other issues, and were described by the likes of Hippocrates and Aristotle4.  In an aesthetic rather than utilitarian vein, precious corals have been used for decorative uses for thousands of years5.  Even throughout the second half of the 20th century, precious corals were harvested sporadically offshore of Oahu, Hawaii, among other global locales particularly on other Pacific islands and in the Mediterranean Sea.  The fishery in Hawaii includes some of the oldest animals on Earth; specimens of gold (Gerardia sp.) and black coral (Leiopathes sp.) have been radiometrically dated to be over 2700 years and 4200 years old, respectively 6.

A recent study delved into the oft-overlooked ornamental invertebrate fishery in Florida7.  Many aquarium hobbyists are no longer simply displaying fish-only tanks, opting instead to recreate microcosms of reef ecosystems.  The live coral (and ‘live rock’) trade alone is worth 200-330 million USD annually.  Little attention has been given to the impact that this coral and invertebrate collection has on Caribbean reefs, which sadly are among the worst off.  By Florida law, all commercial marine fisheries collections are to be reported; these data are compiled by the Florida Fish and Wildlife Conservation Commission.  Andrew Rhyne and colleagues used records from 1994-2007 to access the scale and general nature of this multi-species ornamental fishery.

Total landings were found to have increased drastically in this 13-year period, increasing by over half a million individuals each year.  Collectors do not target various invertebrate taxa uniformly:  in 2007, the top 15 species collected represented 92% of all landings; in 1994, the top 15 represented 88%.  The composition of these catches has shifted markedly due to the shift from purely ornamental specimens to species that can provide biological controls in reef tanks; however, fishing pressure on nearly every species has increased.  There’s also the question of removing individuals which perform an ecosystem function out of that environment.  6 million individuals were collected in 2007 that were considered grazers, which is more than double the landing reported for curio and ornamental purposes combined (figure below).  Grazers are popular because they control algal growth in tanks.  But they also provide this same ecosystem function in the ocean.  Less grazers means a less resilient reef and one that is increasingly likely to being overgrown by macroalgae.

Ecosystem processes and services in FLML invertebrates. Inlays show % of the total catch. From Rhyne et al. 2010.

Rhyne et al. propose that it may be most useful to manage this fishery by 1) species complexes, to avoid taxonomic ambiguities, and 2) considering single-species management strategies for the top 15 species collected and multi-species based strategies for the reminder.  Strangely, the gloomy economic climate seems to provide an apt time to implement new regulations.  The researchers note that

“Given the stark outlook for the global economy at the present time, and given that marine home aquaria are ‘‘luxury’’ expenditures, growth in ornamental fisheries is expected to slow or decrease. While industry demand is slow, a limited window of opportunity is open where management policies can change without immediate disruption of economic livelihood.”

Considering diversity and landings, Florida’s ornamental fishery is ranked third worldwide, only behind Indonesia and the Philippines. To date, this fishery operates with a licensing scheme under which most fishing is not affected by any current regulations.  For example, not granting any new licenses and reducing current licenses has only removed small-scale or inactive organizations.  The fact that only a few licenses are responsible for most of the fishery compounds this problem.  Can a collapse be avoided?  Hope seems to exist but the ultimate outcome is uncertain.  Fishermen within the Florida Keys Marine Sanctuary are calling for stricter regulations and the implementation of monitoring programs.  This work highlights the need to consider ornamental fisheries in the conservation and management of our marine resources.
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1. Helfman GS (2007) Fish Conservation: A Guide to Understanding and Restoring Global Aquatic Biodiversity and Fishery Resources. Island Press. Note that this is a secondary source (textbook) that discusses a multitude of papers in the primary literature. Most of the background on global fisheries discussed here was found within this work.
2. Myers RA, & Worm B (2003). Rapid worldwide depletion of predatory fish communities. Nature, 423 (6937), 280-3 PMID: 12748640
3. Jackson, J. (2008). Colloquium Paper: Ecological extinction and evolution in the brave new ocean Proceedings of the National Academy of Sciences, 105 (Supplement 1), 11458-11465 DOI: 10.1073/pnas.0802812105
4. Voultsiadou E (2010). Therapeutic properties and uses of marine invertebrates in the ancient Greek world and early Byzantium. Journal of ethnopharmacology, 130 (2), 237-47 PMID: 20435126
5. R Grigg (1993). Precious Coral Fisheries of Hawaii and the U.S. Pacific Islands Marine Fisheries Review, 55 (2), 50-60
6. Roark EB, Guilderson TP, Dunbar RB, Fallon SJ, & Mucciarone DA (2009). Extreme longevity in proteinaceous deep-sea corals. Proceedings of the National Academy of Sciences of the United States of America, 106 (13), 5204-8 PMID: 19307564
7. Rhyne, A., Rotjan, R., Bruckner, A., & Tlusty, M. (2009). Crawling to Collapse: Ecologically Unsound Ornamental Invertebrate Fisheries PLoS ONE, 4 (12) DOI: 10.1371/journal.pone.0008413

Symbiotic Foreclosure: coral bleaching predictions and a potential acclimation mechanism

NOAA—the National Oceanic and Atmospheric Administration—issued a press release on September 22nd declaring coral bleaching likely in the Caribbean.  NOAA reports that:

With temperatures above-average all year, NOAA’s models show a strong potential for bleaching in the southern and southeastern Caribbean through October that could be as severe as in 2005 when over 80 percent of corals bleached and over 40 percent died at many sites across the Caribbean.

Comparing future bleaching outcomes to 2005 is an especially bad sign. 1998 and 2005 were the most thermally destructive years for coral reefs since record keeping began in 1880, damaging reefs in the Indian Ocean, Western Pacific and the Caribbean1. Reefs in the Indian Ocean and in parts of the Pacific have begun to recover after the particularly well-known 1998 bleaching event, yet the situation in the Caribbean has worsened due to regional mass bleaching, and the general lowering of reef resilience through sedimentation, nutrient pollution, and over-exploitation1.


Shallow corals are capable of feeding heterotrophically, that is, snagging bits of organic matter and plankton out of the watercolumn, but they overwhelming make their living by playing host to photosynthetic, intracellular dinoflagellate algae, known collectively as zooxanthellae (Symbiodinium spp.). These algal symbionts can be biochemically compromised by heat stress and can then be expelled by the host, an event known as bleaching; the coral will inevitably starve unless it can recruit more symbionts.  Bleaching can be caused by other factors as well2, e.g. heat/cold shock, heavy metals, prolonged darkness, among others; however, thermal stress appears to be a main factor, especially in the regional-scale bleaching that NOAA is predicting. The connection between increased seawater temperature and bleaching has been confirmed by laboratory studies and observed in the field3, particularly after El Nino/Southern Oscillation climatic events.  A recent article published in the New York Times generated some discussion on the NOAA-administered Coral List in the past couple of days in regards to designating 2010 as an El Niño or La Niña year.  We’ve been in a La Niña (characterized by cool temperatures in the Pacific) since May, but earlier in 2010, an El Niño (characterized by warm temperatures) was present.

The planet, including the ocean, is warming4.  One possible mechanism for corals to adapt to hotter climate regimes is the idea of ‘symbiont shuffing.’  Not all types of zooxanthellae are created equal. Some groups—namely type D—are better at managing higher temperatures without expulsion from the host coral; more importantly, shuffling to type D has resulted in increased thermal tolerance in at least one species of scleractinian (stony, reef-building coral).  But don’t excited yet:  we do not know if this symbiont switching is widespread, if particular coral species are capable of this at all, or if this phenomenon may incur some sort of physiological cost.  A study in PLoS ONE5 on the Great Barrier Reef worked to clarify this last tenet.  Jones and Berkelmans found in lab experiments that Acropora millepora corals grew 29% slower with type D symbionts, than those with C2 symbionts—a thermally sensitive type.  In the field, this skeletal growth difference was 38%.  If reefs acclimate via this mechanism, growth rates would be depressed if this trend was widespread among reef-building species.  How quickly certain types of corals grow is an extremely important facet of recovery after a disturbance; the authors point out that without timely coral regrowth, phase shifts can occur to an algal-dominated states within coral reef ecosystems.  This has happened at locales in the Caribbean, albeit for different reasons (the dieoff of a dominant grazer).  So although potentially beneficial in terms of adapting to increased temperatures, a switch to type D does not seem to be a boon to coral physiology, at least in terms of growth. A bleaching event during this study dropped growth rates across all symbiont types by more than 50% for a year and a half, showing (not surprisingly) that loss of their zooxanthellae has a larger impact than shuffling zooxthanellae types. Thermal stress coupled with the physiological cost associated with this acclimation mechanism are expected to interact, possibly further compromising reef resilience in a warmer world. Something that I’d like to add is that this shuffling is not known to ameliorate the effects of ocean acidification, which refers to the alteration of seawater chemistry (really a change in the carbon cycle itself) in a way that causes coral calcification to become more energetically difficult.

CO2 levels are expected to exceed 500 ppmv by 21006.  This level of change has not been seen in at least the past 420 thousand years, perhaps longer6.  The long-term fate of these extremely biodiverse oceanic centres is yet unknown. These animals are enormously resilient in one form or another on evolutionary and geological timescales, but the sheer rate of this environmental change is huge (2-3 orders of magnitude faster than most changes in the past 420 kyr6) and we may see drastic changes in the reef ecosystem functionality well within this century.

This post was chosen as an Editor's Selection for ResearchBlogging.org

Image 1: The Batman Comic Generator (this particular representation was inspired by A Replicated Typo‘s icon at Research Blogging).  Image 2:  Bleaching fire coral at Flower Gardens (Gulf of Mexico). NOAA-FGBNMS).

References:

1.  Wilkinson C (ed) (2008)  Status of coral reefs of the world: 2008. Global Coral Reef Monitoring Network and Rainforest Research Centre, Townsville, Australia, 296 p.
2.  Douglas AE (2003). Coral bleaching–how and why? Marine pollution bulletin, 46 (4), 385-92 PMID: 12705909
3.  Hoegh-Guldberg O (1999) Climate change, coral bleaching, and the future of the world’s coral reefs. Marine and Freshwater Research 50:839-866
4.  Solomon SD et al. (eds) (2007) Climate change 2007:  The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge UK and New York USA.
5. Jones, A., & Berkelmans, R. (2010). Potential Costs of Acclimatization to a Warmer Climate: Growth of a Reef Coral with Heat Tolerant vs. Sensitive Symbiont Types PLoS ONE, 5 (5) DOI: 10.1371/journal.pone.0010437
6. Hoegh-Guldberg O, Mumby PJ, Hooten AJ, Steneck RS, Greenfield P, Gomez E, Harvell CD, Sale PF, Edwards AJ, Caldeira K, Knowlton N, Eakin CM, Iglesias-Prieto R, Muthiga N, Bradbury RH, Dubi A, & Hatziolos ME (2007). Coral reefs under rapid climate change and ocean acidification. Science (New York, N.Y.), 318 (5857), 1737-42 PMID: 18079392

Emergent Conservation Issues

A recent article (Sutherland et al. 2010) from Trends in Ecology and Evolution provides insight on several emerging research areas through a practice called ‘horizon scanning’—really, a sciency way to say that the authors shortlisted environmental issues that they collectively felt were important, merited further discussion, and could effect biodiversity.  The point is made that science needs to occur before critical policy decisions are made.  Admittedly, this is a fairly obvious statement; but it’s important that we be reminded of it.  For example, if a fisheries council realizes that their country’s commercial fishers are rapidly depleting a certain fish stock, it would really be nice to know facets of that organism’s life history (e.g. time to reproductive maturity, lifespan, etc.) so that intelligent management decisions could be made before the fishery potentially collapses.  The authors discuss 15 issues on the horizon, so to speak.  All are quite interesting and have mostly been understudied, so let’s have a look…

Microplastic pollution:  Plastic resins comprise the majority of general litter and over time it degrades to small particles.  The effects on wildlife are largely unexplored, but hormonal effects are known and a disproportionate impact on filter-feeding sessile organisms is likely.  Alan Weismann gives an eye-opening perspective on the history and implications of this, especially in the North Pacific Gyre, in his book The World Without Us.

Nanosilver in wastewater:  Nanosilver refers to tiny particles of silver that are used mainly as an antimicrobial and could be potentially used in utensils, air conditioners, and medical devices.

Synthetic meat:  Pretty much what it sounds like…meat grown from muscle stem cells in a lab.  Costs are prohibitive at this point (this study cites figures between 10,000 and 100,000 USD per kilogram).  This has implications for reducing livestock produced greenhouse gases and relieving pressure on exploited fish stocks, as well as land-use changes.  The authors warn of possible adverse effects on plant life dependent upon grazing, however.  Plus, they don’t know if anyone would actually want to eat the stuff.

Artificial life:  Essentially, designing genomes…a topic of enormous ethical and environmental consequence.

Stratographic aerosols:  Geoengineering is increasingly being thrown around in academic circles and in the news.  This particular idea has to do with injecting particles into the upper atmosphere to reflect sunlight, sort of a planetary sun block.  This study concedes that such an approach could lower temperatures, but also warns that it would be ineffectual for reducing the atmospheric carbon load or mitigating ocean acidification.  Some aerosols could even reduce the pH of precipitation and increase ozone destruction, while virtually all could modify regional climates. Pretty gloomy possible outcomes for something that’s supposed to help, if you ask me.  We can all agree that something needs to be done, but I personally doubt that large-scale geoengineering within earth systems that are not even totally understood should be considered without further research.

Biochar:  Burning organic material without oxygen produces biochar.  The idea is that such a mechanism would sequester carbon (decomposing plants release carbon) and mitigate climate change.  However, to have any real effect It would have to be used globally.  Questions remain regarding the effect on biodiversity.

Deoxygenation of the ocean:  Dissolved oxygen in certain regions of the world ocean has declined since mid-1900s.  This spread of anoxia/hypoxia is predicted to get worse with our current carbon emissions.  This water condition is having and will continue to have detrimental effects on marine life and may restructure marine food webs.

Changes in denitrifying bacteria:  These bacteria convert anthropogenic nitrogen (via fertilizer runoff into rivers, etc., etc.) to molecular nitrogen which then is reincorporated into the atmosphere.  However in some cases, these communities, especially it seems in estuaries, have become nitrogen fixing, rather than denitrifying, effectively becoming a source of nitrogen, rather than a sink, with possible ramifications in ocean acidification or the production of nitrous oxide, a greenhouse gas.

High-latitude volcanism:  Step 1:  Glacial melting.  Step 2:  There’s a volcano!  Okay, maybe not that dramatic, but there is volcanic activity under glaciers that’s being uncovered.  Volcanic activity could speed up glacial melting, leading to potential sea level rise.

Invasive Indo-Pacific lionfish:  Lionfish are an invasive species now found from Rhode Island to Columbia, occurring in far greater densities here than in their natural range.  They are protected by a barrage of poisonous spines and have the potential to reduce the recruitment of coral reef fish (through consuming larvae).  Their effects on the reef ecosystem dynamics are largely unknown.

Trans-Arctic dispersal and colonization:  The Arctic in past climatological regimes (e.g. mid-Pliocene) has acted as a dispersal barrier and a controlling force in terms of marine species biogeography.  As the waters warm and the ice melts, species may be able to move between the Atlantic and Pacific oceans via the Arctic, with the capacity to alter long established ecosystems.  Increased shipping activity through the Northwest Passage is likely to worsen this issue.

Assisted colonization:  A significant portion of terrestrial species is predicted to be at risk of extinction by 2050 due to climate change.  Assisted colonization refers to the controversial practice of moving organisms to locations that may be more climatologically suitable than where they naturally occur, due to warming in their original locales.

Possible impact of REDD on non-forested ecoystems:  REDD (the UN’s Reducing Emissions from Deforestation and Forest Degradation program) focuses on increased forest protection, which may in turn cause more pressure to be put on less-protected systems, which may also have high carbon sequestration potential.

Large-scale international land acquisitions:  This refers to countries buying up large amounts of farmable land in order to ensure food supply.  Despite having potential positive impacts on developing countries in terms of supplying capital, technology and markets, this study warns of the impact of land-use conversion and intensive agriculture on biodiversity.  Locals losing access to their own natural resources is also a possible concern.

Mobile-sensing technology:  Using the cellphones of the masses to provide real-term data regarding the environment.

All in all, these topics have largely been overlooked, yet seem destined to become conversation issues in the not-so-far-off future (well, some already are) and therefore research should lead policy decisions, rather than the other way around.

 

Image:  Common lionfish (Pterois volitans) from Jens Peterson on Wikimedia Commons.

This post was chosen as an Editor's Selection for ResearchBlogging.org
ResearchBlogging.org

Sutherland, W., Clout, M., Côté, I., Daszak, P., Depledge, M., Fellman, L., Fleishman, E., Garthwaite, R., Gibbons, D., & De Lurio, J. (2010). A horizon scan of global conservation issues for 2010 Trends in Ecology & Evolution, 25 (1), 1-7 DOI: 10.1016/j.tree.2009.10.003