Effects of offshore tuna farming on benthic assemblages in the Eastern Mediterranean

Abstract

The spatial effects of 2 tuna farms on the benthic community were investigated in the Eastern Mediterranean during the fattening period. The impact on benthic fauna was assessed in the vicinity of the fish farms (beneath and at various distances from the cages) using a variety of benthic indicators used for the implementation of the EU Water Framework Directive (WFD). There was a general consensus that most of the samples (95%) were acceptable, i.e. of 'good' or 'high' ecological status. The biotic indices were also compared between 2 different mesh sizes, total (resulting from the sum of the fractions of 1 and 0.5 mm mesh fractions) and 1 mm mesh, in order to assess the variability of the results. The indicators showed the same pattern between the 2 different sieve mesh sizes. The variability in the ecological status assigned by each indicator was also examined among the replicates taken from each station. Our results showed that one replicate is not sufficient for monitoring purposes, and we suggest obtaining more replicates while using indicators requiring less taxonomic effort for sample processing. Neither fish farm had a significant impact on benthic communities, due mainly to the exposed nature of the study site.

Response of Benthic Macrofauna to Eutrophication in a Mesocosm Experiment: Ecosystem Resilience Prevents Hypoxic Conditions

“…In the context of the European Water Framework Directive (WFD), a series of benthic indicators were developed and have been widely used, including the AZTI Marine Biotic Index (AMBI) (Borja et al, 2000) and its multivariate version M-AMBI (Muxika et al, 2007), the Benthic Index (BENTIX) (Simboura and Zenetos, 2002), the Benthic Quality Index (BQI) (Rosenberg et al, 2004) and the BQI-Family (Dimitriou et al, 2012). As reported in numerous publications (Borja et al, 2003(Borja et al, , 2008Simboura and Reizopoulou, 2007;Gremare et al, 2009;Subida et al, 2012;Karakassis et al, 2013;Moraitis et al, 2013;Simboura et al, 2016), these indices have been found to be suitable tools for assessing the Ecological Status (ES) of coastal marine ecosystems.…”

Assessment of the impact of Atlantic bluefin tuna farming on Adriatic benthic habitats by analysing macroinvertebrate assemblage structure at family level

“…Additionally, TP and TFS were the chemical variables that best reflected the effects of tuna farming on soft sediments. Several studies on the potential environmental impacts of tuna farming have been carried out in the Mediterranean (Aksu et al, 2010;Matijević et al, 2006;Mangion et al, 2014;Moraitis et al, 2013;Vezzulli et al, 2008;Vita et al, 2004), suggesting that the most important factor is sedimentation of uneaten bait, which could lead to anoxic conditions. However, when there is a proper feeding management strategy at the facility, the input of organic matter into the benthos from uneaten bait can be relatively low.…”

Influence of tuna penning activities on soft bottom macrobenthic assemblages

“…Vezzulli et al (2008) assessed the organic waste impact of ABT farming on a variety of water column and benthic habitat attributes, while a study by Šegvić Bubić et al (2011) assessed the influence of a tuna farm on the associated wild fish assemblages. Other studies assessed the food-web effects of tuna farming on trophic linkages (Forrestal et al, 2012) and the emissions that result from the tuna penning industrial activities (Hospido and Tyedmers, 2005) However, few studies have addressed the influence of ABT ranching on the benthic macroinvertebrate assemblages in the vicinity of tuna pens Vita and Marin, 2007;Vezzulli et al, 2008;Moraitis et al, 2013). In particular, studies comparing attributes of benthic assemblages before initiation of tuna penning to after, are lacking.…”