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Acoustic loading of harbor porpoises
Project
Project code: 01HS089
Contract period: 01.08.2008
- 31.07.2005
Purpose of research: Applied research
Acoustic deterrents, so-called pingers, are scheduled for use with nets in European fisheries. The effect on harbour porpoises (Phocoena phocoena) is still unknown. This study examines for the first time the inner ears of Phocoena phocena from German and adjacent Danish waters of the North and Baltic Seas. In cooperation with, and supported by Harvard Medical School, Boston, USA, examinations of the head were conducted by computerized tomography, and the ear region was more closely investigated by means of celloidin histology sections with standard H/E staining. 28 harbour porpoises were sampled, 46.4% of which came from German waters, 53.6% from Danish waters, 71.4% from the Baltic, and 28.6% from the North Sea. Over 60% (17) of all sampled animals were by-caught in nets without pingers. 25% (7) stranded dead, 10.7% (3) stranded alive, but efforts to rehabilitate them failed. One animal was floating in the open North Sea. The Danish wreck fishery was impacted by the heavy decline of cod in the North Sea in 2002. Only harbour porpoise by-caughts from regular nets were accessed. This explains why the impact of pingers on the inner ears of harbour porpoises cannot be estimated at this time. However, basic morphology data from inner and middle ears of harbour porpoises from German and adjacent Danish waters were collected. None of the animals showed intravital atrophies of organ of Corti sensory cells. Several pre-mortem changes were found, such as parasitic infestations and inflammatory reactions, each of which can be a cause of the other. The pathology however is still unknown. Even the common finding of parasites and their effects on hearing is still unknown. Additional changes of the acoustic fat of the lower jaw, reduced 8th cranial nerve and soft tissue deposits, among others, should also be investigated and analysed based on a larger sample.
Section overview
Subjects
- Marine fisheries
