Pingers reduce harbour porpoise bycatch in Norwegian gillnet fisheries, with little impact on day-to-day fishing operations

A field trial was conducted to determine the effect of acoustic deterrent devices (ADDs, or pingers) on harbour porpoise (Phocoena phocoena) and harbour seal (Phoca vitulina) bycatch in three Norwegian commercial gillnet fisheries targeting cod (Gadus morhua), saithe (Pollachius virens) and monkfish (Lophius piscatorius). Catch data on 3500 net-km-days were collected by 8 fishing vessels operating gillnets in high bycatch regions over two years. A total of 20 harbour porpoises and 9 harbour seals were bycaught, with 19 harbour porpoises and 6 harbour seals taken in control (non-pingered) nets. Bycatch was modelled using a generalized additive mixed modelling approach and fitted with penalized maximum likelihood. Modelling results indicated that using pingers on gillnets reduced the risk of bycatching a harbour porpoise by an estimated 94% (95% confidence interval CI 77–100%) compared to ordinary pinger-free nets. The effect of pingers was not significantly different between different fisheries. The pingers also had no significant effect on catch rates of fish (Wilcoxon rank sum test, p = 0.24) or harbour seals (Wilcoxon rank sum test, p = 0.19). Self-reported pinger-associated extra time costs on day-to-day fishing operations were low, averaging about 2.8 min per operation. These results add to a growing body of scientific evidence that pingers can lead to substantial reductions in harbour porpoise bycatch rates in gillnet fisheries, and that extra time costs associated with operating nets with pingers are low.Pingers reduce harbour porpoise bycatch in Norwegian gillnet fisheries, with little impact on day-to-day fishing operationspublishedVersio

Reduction of algal vegetation in Helgeland coastal waters

Reduced densities of Laminaria have been reported from coastal waters in Sør-Trøndelag, Nord-Trøndelag and Nordland counties. A provisional study of algal vegetation and benthic fauna was made by diving west of Vega in Helgeland, Nordland county (position 65°41'N 11°43 'E), 17-19 October 1979. The study revealed a significant difference in sublittoral density of sea urchins between three locations selected for abundant, scattered and no Laminaria growth. Strongylocentrotus droebachiensis dominated over Echinus esculentus at all three locations. The lowest sea urchin density was found at the location with abundant Laminaria, and a high density of sea urchins at the location with no or scattered Laminaria. It is therefore presumed that grazing by increasing numbers of sea urchins is a major factor causing a reduction of Laminaria. The catfish (Anarhichas lupus) may be the most important predator on sea urchins in these waters, and the catfish is preyed upon by seals. It is therefore suggested that increasing local stocks of grey seals (Halichoerus grypus), may have influenced the catfish abundance, and thus allowed the sea urchins to increase with a subsequant detrimental effect on the vegetation of Laminaria

Recoveries in Norway of grey seals, Halichoerus grypus tagged in Great Britain

Since tagging of grey seals in Great Britain was initiated in 1951, a total of 61 seals has been recovered in coastal Norwegian waters. Most of the recovered seals had been tagged at the Orkney (35 recoveries) and the Farne Islands (17 recoveries) and captured in fishing gear on the southwestern coast of Norway. Recovery rates are highest from the Orkney and Shetland breeding stocks (about 12 and 10 per thousand) . Among the total of 61 recoveries, 58 were recovered within six months after tagging, two after three years and one after five years. We assume that after arriving in coastal Norwegian waters, the British grey seals are equally vulnerable to recovery as Norwegian grey seals of the same age. Using a known recovery rate of Norwegian grey seals, the total immigration from Great Britain is estimated to be about 14300 seals through the period 1960-1981 with an average of about 650 seals per year. There is no indication in the available information that British grey seals are recruiting to Norwegian breeding stocks or establishing new breeding colonies on the Norwegian coast

Count of common seals (Phoca vitulina) at Hvaler in outer Oslofjord, Norway, 1983

A survey was carried out on 10 August 1983 in order to count common seals, and all suitable haul out sites in the outer Hvaler area were examined. A total of 255 common seals were recorded in the area. The observed seals were almost exclusively one year old and older moulting seals. One immature grey seal and one adult male grey seal were observed among the common seals

Low anthropogenic mortality of humpback (Megaptera novaeangliae) and killer (Orcinus orca) whales in Norwegian purse seine fisheries despite frequent entrapments

Fishery inspector logbooks were used to estimate fishing gear interaction rates for humpback (Megaptera novaeangliae) and killer (Orcinus orca) whales in Norwegian purse seine fisheries for herring from 2011 to 2020. Estimated rates were applied to fisheries data to estimate fleet-wide totals. Estimates showed that in a 10-year period, a total of 78 humpback whales, 95% CI [41, 145] and 100 killer whales, 95% CI [63, 176] were entrapped in purse seines. Most whales were disentangled alive, with an estimated mortality of 5%, CV 0.69, 95% CI [0.0, 11.8] and 6%, CV 0.48, 95% CI [0.3, 11.9], respectively. The average yearly mortality over the study period was thus approximately 0.60 killer whales and 0.39 humpback whales corresponding to 0.008% and 0.007% of the respective abundance estimates for these whale species in Norwegian waters. Given the Potential Biological Removal sustainability limits of 98 humpbacks and 161 killer whales per year, it may be concluded that, by itself, the average yearly mortality incurred by these whale populations by Norwegian fisheries does not constitute a significant risk to either of these species, but bycatch in Norwegian purse seine fisheries may not be the only source of anthropogenic mortality.Low anthropogenic mortality of humpback (Megaptera novaeangliae) and killer (Orcinus orca) whales in Norwegian purse seine fisheries despite frequent entrapmentspublishedVersio

Diet composition and biomass consumption of harbour seals in Telemark and Aust-Agder, Norwegian Skagerrak

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Investigations of common seals (Phoca vitulina) and grey seals (Halichoerus grypus) in Rogaland and Finnmark counties Norway, in 1981

The outer coastline from Bømlafjorden to Jæren and Lysefjorden in Rogaland were surveyed 29 May-5 June. Another survey was carried out on the coast of Finnmark from Varangerfjorden to Sørøya 26 June-7 July 1981. In Rogaland a total of 75 common seals was recorded. The seals were most abundant in the Kvitsøy-Håsteinen area (38 seals) and in Lysefjorden (27 seals). In Kongsfjorden, Finnmark, 23 pups were observed (corresponding to a total stock in excess of 100 seals). Another colony of common seals was found at Sørøya (20 seals), and common seals were also seen in Varangerfjorden, Tanafjorden and Kobbfjorden. Concentrations of grey seals were found in the Espevær-Utsira area (36 seals) and at Kjør (60 seals) in Rogaland, and in Syltefjorden (40 seals) and at Sørøya (70 seals) in Finnmark. Scattered seals or small groups were also seen outside these areas. Due to adverse weather conditions very few common seals were observed during the surveys, and the numbers recorded probably are significantly lower than actual stocks. So far, the available data are insufficient to assess the stocks of common seals in Rogaland and Finnmark. However, the observations of grey seals indicate an increase from assessed stocks in the early 1960-ies. Stomachs from a total of ten common seals and nine grey seals were examined during the surveys. Haddock, sand eels and flatfishes were identified in the common seals, while the grey seal stomachs contained catfish, saithe, haddock, herring, lumpsucker, sand eels and flatfishes. The maximum volume of stomach contents found in a common sea1 was 4 1, and volumes up to 6 l were recorded in grey seals. The average infestation of parasitic nematodes in the stomachs of examined common seals was 64 worms, while the average infestation in the grey seals was 492 worms. An aerial survey to count whitecoated grey seal pups was carried out 7 November in Rogaland. No pup or concentration of grey seals was observed, and if grey seals do produce pups in Rogaland, pupping probably occurs in early Octoher. Aerial surveys were also carried out along the coast of Finnmark 28 and 29 October. No grey seal pup was found, and the surveys were repeated 17-20 November. At that time concentrations of grey seals were ohserved on shore at the presumed breeding localities. It therefore seems likely that pupping in Finnmark occurs later than 20 November