Tasmania, an Australian island state 150 miles off the southeastern part of the continent, shares some surprising similarities with Maine. It has an important lobster fishery and, like Maine, is categorized as a climate change “hotspot” with waters also warming at a rate well above the global average.
The Tasmanian lobster fishery targets the southern rock lobster (Jasus edwardsii). The fishery was transferred to individual transferable quotas (ITQs) in 1998, with annual landings of around 3 million pounds and a total landings value, in 2008, of around $57 million.
Do the back-of-the-envelope math and you identify one key difference between Tasmania’s and Maine’s lobster fishery: At around $20 per pound, Tasmanian lobstermen are receiving a much higher price than Maine lobstermen.
But back to the science: At approximately four times the global average, Tasmania’s temperate waters are warming faster than anywhere else in the southern hemisphere. The Gulf of Maine, part of the northwest Atlantic Ocean, is also experiencing some of the fastest warming in the world. Like their counterparts in Maine, Tasmanian scientists and fisheries managers are trying to understand the biophysical, social and economic implications of this rapid warming.
One of the impacts of warmer than usual waters here in Maine has been changes in the timing of life-cycle events, like molting (when a lobster drops its hard shell in order to grow larger). In 2012, our lobsters molted around three weeks early due to the abnormally warm water over the previous seven to ten months, which constituted the most intense ocean heat wave in the northwest Atlantic in the last 30 years. In Tasmania, the southern rock lobster also has experienced earlier-than normal molt timing.
Other, more difficult to observe critical processes like spawning and larval settlement of marine species also are strongly affected by temperature. Scientists in both hemispheres are measuring declines in settlement of larval lobsters, which may be related to rising sea temperatures.
Another more widespread implication of warming is the changing distribution of fish, invertebrates and even marine algae. Because Tasmania is located in the southern hemisphere, a migration of marine species toward the pole occurs in a southward direction, whereas species in New England are moving north to escape the heat. In Tasmania, the southern range expansion of the long-spined sea urchin, Centrostephanus rodgersii, is causing serious problems for their lobster fishery. This urchin has much longer spines than the green sea urchin, formerly abundant in the Gulf of Maine, but like its distant relative, it is also an important herbivore.
In Australia, these long-spined sea urchins are effective grazers, maintaining “barrens,” or areas free of kelp and other marine algae. As the urchins expand southward into newly hospitable, warmer water, the seafloor ecosystem is shifting from a kelp-dominated system—one that is excellent habitat for lobster—to seaweed-free areas.
Large lobsters are one of the few effective predators of the spiny urchin, but fishing has removed many of the largest lobsters from the water, creating easier survival for urchins, which leads to further degradation of the lobster habitat.
Tasmania is struggling not only with the presence of a new ecosystem “engineer,” but with the questions of whether or how to change lobster fishing regulations in order to leave more urchin predators in the water.
One promising initiative is a new early warning system to identify these range shifts in order to inform proactive management of emerging species.
Dr. Greta Pecl, a senior research fellow at the Institute for Marine and Antarctic Studies at the University of Tasmania, and a team of other researchers developed an online database and mapping resource that allows members of the public, primarily commercial and recreational fishermen and scuba divers, to submit observations of marine species occurring outside of their previously normal ranges. The project, called Redmap (Range Extension Database and Mapping project, www.redmap.org.au), allows users to submit geo-tagged photographs that are then verified by a scientist specializing in the observed species.
The project has been successful in attracting many citizen science participants to help track the impacts of a shifting marine climate. Interestingly, a 2009 study of rock lobster fishermen by Pecl found that about 80 percent of harvesters in Tasmania do not believe that climate change is happening. Despite this hurdle, fishermen generally love talking about interesting things that came up in their gear, and scuba divers love taking photos.
On the positive side, much like Maine fishermen are now seeing species that are typically found farther south—such as longfin squid, black sea bass, and even blue crabs—new opportunities for Tasmanian commercial and recreational fishermen may emerge. Among the species moving south are tropical and sub-tropical fish such as blue marlin, mahi mahi, yellowfin tuna and cobia. But in both states, on opposite sides of the world, fishermen, researchers and fishing communities remain concerned about how other new fisheries could possibly replace a highly lucrative lobster fishery.
Dr. Heather Deese is an oceanographer and the Island Institute’s vice-president for strategic development. Dr. Susie Arnold is an ecologist and marine scientist with the organization.