Influence of tuna penning activities on soft bottom macrobenthic assemblages

Mangion, Marija; Borg, Joseph A.; Thompson, Richard; Schembri, Patrick J.

Influence of tuna penning activities on soft bottom macrobenthic assemblages

2014

Mangion, Marija | Borg, Joseph A. | Thompson, Richard | Schembri, Patrick J.

The influence of tuna penning on soft bottom habitat present in the vicinity of tuna pens and at distances 200m and 1.5km away, was assessed by comparing attributes of macroinvertebrate assemblages and sediment quality before (November 2000, March 2001) and after (November 2001, April 2002) initiation of the activity. Results from November 2001 indicated a significant increase in sediment organic carbon and organic nitrogen, and a non-significant increase in the abundance of Capitellidae in the vicinity of the cages. Similar results were obtained 200m from the cages but not 1.5km away, where the only change was a significant increase in organic nitrogen in sediment. Results from April 2002 indicated no significant change in sediment organic carbon and organic nitrogen, however, mean sediment grain size decreased significantly in the immediate vicinity of the cages. Changes in attributes of the benthic assemblages and sediment resulted from accumulation of uneaten feed-fish on the seabed.

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