Protected Species and Marine Aquaculture Interactions

Bottlenose dolphin
An ecosystem modeling approach in the Ionian Sea
concluded that increased productivity from fish farm nutrients
had positive impacts to bottlenose dolphin populations
in the region (Piroddi et al. 2011). The increase of
fish farms was the main explanatory variable that was successfully
used to reconstruct the observed trends in dolphin
biomass and distribution from 1997 to 2008. In oligotrophic
waters, rapid transfer of nutrients up the food
web has been shown to increase commercial fish biomass,
and fish farms are known to act as attracting devices for
forage fishes (see review in Price & Morris 2013). A study
in central Greece found that bottlenose dolphin occurrence
was higher in areas within 5km of fish farms and lower at areas more than 20km
from farms (Bonizzoni et al. 2014). Observed dolphins were thought to be foraging,
often within 10m or less of the fish cages and did not appear to avoid farm structures
or noise from farm activities. Interestingly, not all fish farms held equal appeal. Dense
farm aggregations and gentler slope had a higher probability of dolphin occurrence.
Interviews with the farm employees revealed dolphins were not considered a threat
and ADDs are not used in this area.
In Scotland, detectors were placed at salmon farms and reference sights to monitor
porpoise activity and response to ADDs (Northridge et al. 2010). Generally, porpoises
avoided farm areas when ADDs were turned on but returned quickly when they
were deactivated. Some animals were observed foraging near farms with active ADDs,
especially in areas where the devices had been deployed for some time. Concerns are
Common dolphin
Protected Species & Mussel longline aquaculture interactions | 29