Use stiffened materials or increase tension of fishing gear
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
Using stiffened materials or increasing the tension of fishing nets, ropes or lines may reduce the risk of marine and freshwater mammals becoming entangled. However, tensioned vertical ropes may cause injuries to mammals that come into contact with them (Baldwin et al. 2012).
For another intervention that may involve stiffened gear, see Use acoustically reflective fishing gear materials.
Baldwin K., Byrne J. & Brickett B. (2012) Taut vertical line and North Atlantic right whale flipper interaction: experimental observations. University of New Hampshire and Blue Water Concepts.
Supporting evidence from individual studies
A controlled study in 2009–2010 of a pelagic area in the South Atlantic Ocean, off the coast of Buenos Aires, Argentina (Bordino et al. 2013) found that using stiffened fishing nets did not reduce the number of Franciscana dolphin Pontoporia blainvillei entanglements compared to conventional nets. Entanglement rates of Franciscana dolphins did not differ between stiffened and conventional nets (both 0.08 dolphins/haul). Catch rates of the three main target fish species also did not differ between net types (whitemouth croaker Micropogonias furnieri, striped weakfish Cynoscion guatucupa, king weakfish Macrodon ancylodon; see original paper for data). Monofilament nylon gill nets of two types (nets made from a stiff grade of nylon and conventional nets; number of each not reported) were deployed in 150 locations by a fishery. The nets were sampled 1–19 times resulting in 273 hauls of stiffened nets and 279 hauls of conventional nets. An observer on board each of three fishing vessels retrieving the nets recorded the number of entangled dolphins within each of 552 hauls between October 2009 and March 2010.Study and other actions tested