Protected Species and Marine Aquaculture Interactions

Whale's tail
Winn et al. (2008) used flippers and fluke tissues from adult
and juvenile right whales, and a humpback whale collected during
necropsy to assess relative impacts to the tissue under varying types
of laboratory simulations of synthetic lines like those used in fisheries
for float and ground lines. The calf tissue was most vulnerable,
the adult right whale was most resilient, and the humpback
tissue was intermediate. Baldwin et al. (2012) conducted lab and
field experiments with life-sized models of right whale flippers to
test how taut versus slack vertical 5/8 lines, such as those used for
floating buoys to mark fishing gear like lobster pots, might interact
differently with whale flippers. The results of the study suggested
that increased line tension (around 325lbs in the trials) has the potential
to cause significant laceration and perhaps embedment of line into flippers,
even with only glancing contact. Making fishing gear more visible and developing
rope-less fishing gear have been suggested to reduce entanglement (Robbins & Kraus
2011). Both approaches would likely be advantageous in aquaculture operations as
well. While fishery gear may not be as effective at catching target species if it is highly
visible, this should not be an impediment to development of high visibility aquaculture
technology. 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.
ADDs have been deployed in both fishery and aquaculture settings (see previous
discussion of efficacy at fish farms) to avoid harmful interactions with marine mammals.
In both sectors, results have been mixed. The range of effectiveness of ADDs
in aquaculture is discussed previously. Pingers have been found to be effective at decrease
in bycatch of marine mammals but are not 100% effective (Karp et al. 2011,
Waring et al. 2012, 2015). However, pingers in gillnets have been found ineffective at
deterring humpback whales (Harcourt et al. 2014), suggesting that, as with aquaculture,
effectiveness of ADDs is variable and species specific.
Gear modifications and deterrents have also been investigated as methods to reduce
sea turtle bycatch in fixed gear. These have been the focus of discussions at several
workshops (NMFS 2008b, Gilman 2009, NMFS & ASMFC 2013, Wiedenfeld
et al. 2015). The workshop reports summarize the research to date and the potential
mitigation tools identified. Gear modifications proposed, and in many cases tested,
include increasing gear visibility (e.g., illumination), utilizing acoustic deterrents, reducing
net height, eliminating tie-downs, modifying float characteristics, changing
set direction, and reducing the breaking strength of the mesh. Gilman (2009) summarizes
research involving modifications to gillnet and pound net gear designs to reduce
sea turtle catch rates without compromising the economic viability.
In the mid-Atlantic, low profile gillnets have been explored to reduce sea turtle
bycatch in large mesh gillnet fisheries. The low profile nets were 8 meshes high with
24” tie-downs; the control net was 12 meshes high net with 48” tie-downs. No sea
turtles were captured in either net during the study (He & Jones 2013) so the gear
could not be analyzed for bycatch reduction. Recent studies have also evaluated the
56 | ProtEctEd SPEciES and MarinE aquaculturE intEractionS