Action: Use electric fencing to exclude fish-eating birds
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Two before-and-after studies from the USA found that electric fencing reduced the use of fish ponds by great blue herons Ardea herodias and great egrets Casmerodius albus.
Predation by birds at aquaculture facilities (e.g. fish ponds, raceways and shellfish farms) can cause significant commercial loss (Draulans 1987). With increasing protective wildlife legislation, demand for non-lethal, environmentally safe methods of bird exclusion and scaring have increased. Most fish farmers now rely primarily on non-lethal techniques to accomplish control (i.e. to reduce abundance or exclude fish-eating birds in and around the vicinity of fish farms). Control efforts may be optimized by compiling evidence relating to deterrent or exclusion device efficacy, taking into account costs, practicality of use and the possibility of developing integrated strategies (i.e. combining more than one deterrent method). Avian deterrents can be categorised as auditory, visual, chemical, exclusion, habitat modification and lethal (Bishop et al. 2003). Lethal deterrents are not considered here (except where, very rarely, used as part of an integrated approach).
Bishop, J., McKay, H., Parrott, D. & Allan, J. (2003) Review of international research literature regarding the effectiveness of auditory bird scaring techniques and potential alternatives. Department for Environment Food and Rural Affairs.
Draulans, D. (1987) The effectiveness of attempts to reduce predation by fish-eating birds: a review. Biological Conservation, 41, 219–232.
Supporting evidence from individual studies
Before-and-after trials in Mississippi, USA (Mott & Flynt 1995), found that a two-strand electric fence reduced pond use by great blue herons Ardea herodias and great egrets Casmerodius albus by 91%. Five ponds (0.3-2.2 ha in area) containing channel catfish Ictalurus punctatus were tested.
A before-and-after trial in August-November 1996 in Pennsylvania, USA (Tobin et al. 1997), found that electric fencing was fairly effective in deterring great blue herons Ardea herodias from raceways (long, 3-6 m wide fish ponds) at two trout hatcheries (declines from 6-14 birds/h/day and 76-159/h/day to <3 and <58 after electric fencing was erected). Fences comprised two strands of polyethylene tape (1.6 cm wide, 15-30 cm apart). Herons were counted (4 counts/week before and after installation; additional counts to 62 days after installation). Reductions in fish predation were not assessed.
- Mott D.E. & Flynt R.D. (1995) Evaluation of an electric fence system for excluding wading birds at catfish ponds. The Progressive Fish-Culturist, 57, 88-90
- Tobin M.E., Glahn J.F. & Rasmussen E.S. (1997) Electric fencing reduces heron predation at Northeastern trout hatcheries. Proceedings of the Eastern Wildlife Damage Management Conference, 8, 16-19