steelon codends used in commercial fishery, with a nominal mesh size A = 80 mm and A = 100 mm, made of double twines with a thickness of 4.2 mm. The studies covered 6 major fish species.
1. It appears from the study that Antarctic icefish and bumphead notothenia are subject to selection during trawling, although the effectiveness of this process - especially in the latter case - is not satisfactory.
2. Scotia Sea icefish, Chaenodraco wilsoni, and Chionodraco rastrospinosus exhibit a lower tendency to pass through meshes of the codend than Antarctic icefish and bumphead notothenia.
3. The solution to the problem of ensuring selectivity of codends at a sufficiently good level seems possible as a result of the application of webbing with permanently open meshes for codend construction.
4. The most difficult matter will be preparing a codend with proper selectivity properties for South Georgia icefish, because this species exhibits the smallest tendency to escape during the trawling among all the species studied.
Conclusions and observations were in some cases based on a relatively small amount of experimental material.
Further investigations of this problem are necessary since producing selective trawl gear for harvesting Antarctic fish seems crucial from the point of view of conservation of living fish resources on those fishing grounds.
There is no abstract available for this document.
There is no abstract available for this document.
There is no abstract available for this document.
Abstract:
The terrestrial environment of Signy Island, South Orkney Islands, maritime Antarctic, is undergoing rapid and possibly irreversible change caused by a natural biological agent. During the past decade there has been a dramatic increase in the number of Antarctic fur seals Arctocephalus gazella coming ashore on the island during the short summers. It is not known whether significant numbers of seals were present on the island prior to the initiation of commercial hunting in the early 1820s. The impact that the continuing increase of these seals had made on the island's terrestrial and freshwater environments has been sudden and locally devastating. The fragile cryptogam-dominated vegetation has suffered physical damage from which it may be impossible to recover. These seals are also frequenting several of the island's freshtwater lakes which are becoming increasingly eutrophic. The long-term implications of this impact are causing serious concern for the future of the lowland terrestrial and freshwater ecosystems on Signy Island if the fur seal population continues to increase
