Protected Species and Marine Aquaculture Interactions

use of visual deterrents and preliminary work has begun on acoustic deterrents. Wang
et al. (2013) examined the effectiveness of illuminating gillnets with ultraviolet lightemitting
diodes for reducing green sea turtle interactions. The sea turtle capture rate
was reduced by approximately 40% in UV-illuminated nets compared to nets without
illumination. Earlier studies evaluated the use of LED and chemical light stick illumination
to reduce sea turtle bycatch. Mean sea turtle bycatch was significantly reduced
by 60% in the nets illuminated by chemical light sticks and by 40% in the nets illuminated
by LED lights (Wang et al. 2010). These studies suggest that net illumination
may have applications in reducing sea turtle bycatch. Wang et al. (2010) also evaluate
the use of shark shapes on the nets to reduce bycatch. The presence of shark shapes reduced
the mean catch rates of sea turtles by 54% but also reduced target catch.
As described above, vertical lines have the potential to entangle sea turtles. In 2008,
NMFS GARFO sponsored a workshop on interactions between sea turtles and vertical
lines of fixed gear fisheries. One focus of the workshop was on preventing entanglements.
Potential options for reducing entanglements included stiffening the line,
sheathing the line (i.e., encasing lines in rigid or semi-rigid material similar to PVC or
hose), decreasing vertical line density, using sinking breakaway line, and the use of
acoustic and visual deterrents (NMFS 2008b, NMFS 2015). These mitigation techniques
may have potential for reducing sea turtle bycatch in aquaculture gear.
Cooperative field observations and trials, such as those conducted by the NMFS
PRD Gear Research Team, of fishing gear and deployment methods have been conducted
to evaluate in situ the potential for entanglement, and provide opportunity for
fishers and biologists to jointly identify modifications that can decrease entanglement
risk with the minimal impact to catch and safety. A similar approach has been initiated
in Maine to involve lobster fishers in identifying, developing and testing innovative
gear and methods to reduce bycatch and entanglement (McCarron & Tetreault
2012). This cooperative approach to research and development and post-implementation
monitoring (Soykan et al. 2008) is recommended for development of similar approaches
to decrease risk and harm of interactions between protected species and fish
farms. Observer programs have been an important part of understanding and quantifying
fishery gear interactions with protected species (Reeves et al. 2013). Though the
marine aquaculture industry is very small in the United States currently, a similar approach
may be useful for monitoring interactions once it has scaled up.
Further research into the mechanisms behind entanglement and other harmful
interactions would provide valuable insight into how protected species might react to
marine aquaculture gear. More in-depth analysis to discern which protected species
are most prone to entanglement in and collision with fishery gear and in other marine
industry sectors may focus efforts to avoid interactions with commercial aquaculture
sites. A more technical consideration of longline mussel aquaculture gear,
such as tension strength analysis for backbone lines, will provide useful information
for understanding how protected species may interact with farm gear and lead to
effective modifications to decrease harmful interactions. Research to better understand
how marine species perceive farm structures visually and acoustically will likewise
aid in developing strategies to avoid harm.
Additional
information about
vision and color
detection and
response in
protected species
could inform
development of
farm technology
that would be
more visible to
protected species
and, hopefully,
induce avoidance
behavior.
lessons lear ned from Fishery Gear & applications to aquaculture | 57