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November 23, 2014

New Zealand

Lobster—Research, Pollution Not a Problem from Sea Cages


From Abstract: The tropical spiny lobster, Panulirus ornatus, is farmed in floating sea cages in shallow coastal waters in many parts of the Asia-Pacific region.  Despite the rapid expansion of this aquaculture activity, very little is known about the effect of sea cages on the environment. This study combines computer modeling with previous laboratory measures to provide information on benthic carbon deposition and the production of dissolved inorganic nitrogen (DIN) from hypothetical sea cages containing spiny lobsters.


Modeling scenarios were run with two different lobster aquaculture stocking densities (3 and 5 kilograms per cubic meter) and various feed conversion ratios with natural seafood or artificial lobster diets.  Simulations from the model showed that cumulative benthic carbon deposition varied from 0.1 to over 0.8 kilo of carbon per meter square a year, while the mean DIN levels around sea cages ranged from 5.6 up to 25 µg N l−1 and the maximum DIN levels ranged from 10.8 to 165 µg N l−1.  The results showed that feeding lobsters with seafood resulted in a markedly higher benthic carbon loading and release of DIN when compared with artificial lobster feed.  Therefore, the elimination of the use of trash fish would greatly reduce the environmental impacts of spiny lobster aquaculture.  Overall, the effects from spiny lobster aquaculture were spatially localized with the highest concentrations of carbon deposition and DIN directly beneath the sea cages.  Therefore, it seems unlikely that spiny lobster aquaculture in sea cages will cause adverse environmental effects unless the lobsters are heavily stocked and supplied with poor quality feed.


Source: ICES (International Council for the Exploration of the Sea) Journal of Marine Science.  Modeling Carbon Deposition and Dissolved Nitrogen Discharge from Sea Cage Aquaculture of Tropical Spiny Lobster.  Soxi Lee (email, Leigh Marine Laboratory, Institute of Marine Science, University of Auckland, P.O. Box 349, Warkworth, New Zealand), Neil D. Hartstein and Andrew Jeffs.  First published online on October 9, 2014.

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