Jeffs, AHartstein, NLee, So Xi2015-07-0820152015http://hdl.handle.net/2292/26185Spiny lobsters are one of the world’s most valuable seafood species and they have been aquacultured in floating sea-cages since the 1970’s, mainly in Asian-Pacific countries. Despite the growing interest and rapid expansion of spiny lobster aquaculture, knowledge on the potential environmental impacts of this activity are limited. In an effort to begin to understand the environmental impacts of spiny lobster aquaculture, the waste products of two spiny lobsters species (Jasus edwardsii and Panulirus ornatus) were quantified, including the settling velocity of faecal material and DIN output from lobsters of a range of sizes that were fed two dietary treatments (seafood and artificial diet). Quantified particulate (faeces and waste feed) and soluble wastes (dissolved inorganic nitrogen, DIN) were then used as model inputs for a hydrodynamic numerical model to predict potential benthic carbon deposition as well as DIN elevation from hypothetical lobster farming operations. Multiple scenarios with various combinations of stocking density (3 and 5 kg m-3), feed conversion ratios (FCR) using seafood or artificial diet (FCR 1.28 - 28) and three different sizes of farm layout were used in the model simulations. The overall mean settling velocity of faecal strands produced by spiny lobsters (both J. edwardsii and P. ornatus) fed with seafood ranged from 0.30 ± 0.01 (mean ± S.E.) cm s-1 to 0.9 ± 0.05 cm s-1, which was significantly higher than those from lobsters fed with artificial diet (0.22 ± 0.01 cm s-1). However, the settling velocity of faeces did not differ among the lobsters of different sizes for each diet. There was a positive correlation between both the weight and density of faecal strands and their settling velocity. Conversely, neither the length nor the surface area of faecal strands was correlated with the settling velocity. Diet also had significant influence on the DIN excretion. Lobsters of both species (J. edwardsii and P. ornatus) fed with seafood produced more DIN (9.07 ± 0.90 to 12.66 ± 1.98 μg N g-1 hr- 1) than those fed with artificial diet (2.11 ± 0.41 to 11.39 ± 2.36 μg N g-1 hr-1). Hydrodynamic modelling showed that carbon deposition and DIN elevation mainly occurred directly beneath the sea-cages and can be dispersed up to 200 m away from the perimeter of the sea-cage. Modelled results showed that the carbon deposition directly beneath the sea-cages ranged from 0.15 to more than 0.80 kg C m-2 yr-1 while elevated DIN ranged from 5.4 to 25 μg N L-1. Both deposited carbon mass and elevated DIN increased proportionately with higher stocking density and FCR values. The type of diet had the largest effect on both carbon deposition and DIN elevation generated from a lobster farm, with seafood diet producing more extensive impacts than artificial diet. Therefore, the elimination of the use of trash fish as a feed would greatly reduce the environmental impacts of spiny lobster aquaculture. Overall, the results indicate that spiny lobster aquaculture in sea-cages is unlikely to cause adverse environmental impacts on the seabed and water column unless the lobsters are heavily stocked and supplied with poor quality feed.Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher.https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htmhttp://creativecommons.org/licenses/by-nc-nd/3.0/nz/ThesisCopyright: The Authorhttp://purl.org/eprint/accessRights/OpenAccessQ112909592