Variability in spawning frequency and reproductive development of the narrow-barred Spanish mackerel (Scomberomorus commerson) along the west coast of Australia

The narrow-barred Spanish mackerel (Scomberomorus commerson) is widespread throughout the Indo-West Pacific region. This study describes the reproductive biology of S. commerson along the west coast of Australia, where it is targeted for food consumption and sports fishing. Development of testes occurred at a smaller body size than for ovaries, and more than 90% of males were sexually mature by the minimum legal length of 900 mm TL compared to 50% of females. Females dominated overall catches although sex ratios within daily catches vary considerably and females were rarely caught when spaw n ing. Scomberomorus commerson are seasonally abundant in coastal waters and most of the commercial catch is taken prior to the reproductive season. Spawning occurs between about August and November in the Kimberley region and between October and January in the Pilbara region. No spawning activity was recorded in the more southerly West Coast region, and only in the north Kimberley region were large numbers of fish with spawning gonads collected. Catches dropped to a minimum when spawning began in the Pilbara region, when fish became less abundant in inshore waters and inclement weather conditions limited fishing on still productive offshore reefs. Final maturation and ovulation of oocytes took place within a 24-hour period, and females spawned in the afternoon-evening every three days. A third of these spawning females released batches of eggs on consecutive days. Relationships between length, weight, and batch fecundity are presented.

Regional Fisheries Advisory Committee 20th May, 1985

This is the report from the Regional Fisheries Advisory Committee meeting, which was held on the 20th May, 1985. The report contains sections on fishing licence duties in 1986, lead poisoning in swans, Authority investigations into acidity problems in rivers in Cumbria, fishing offences processed, Fish Counter statistics, and the fisheries liaison meeting report. The section on Authority investigations into acidity problems in rivers in Cumbria pays attention on investigations carried out by the University of Lancaster and Freshwater Biological Association about acidity problems, particularly in the Rivers Duddon and Esk since 1980. This section contains biological findings, a chemical sampling programme, results from continuous pH monitors, and catchment liming. The Fisheries Advisory Committee was part of the Regional Water Authorities, in this case the North West Water Authority. This preceded the Environment Agency which came into existence in 1996.

Regional Fisheries Advisory Committee 20th February, 1989

This is the report from the Regional Fisheries Advisory Committee meeting, which was held on the 20th February, 1989. The report contains sections on fishing licence duties, Ombudsman’s Report, net licence allocation criteria, renewal of the Lune and Wyre net limitation order and fishery byelaws. The section on Ombudsman’s Report looks at the complaint against the Authority relating to the allocation of haaf net licences for the Solway Firth for 1988. The Fisheries Advisory Committee was part of the Regional Water Authorities, in this case the North West Water Authority. This preceded the Environment Agency which came into existence in 1996.

Strong, low frequency (decadal) environmental fluctuations during the 20th century in the North Pacific Ocean, on the Washington coast, and in Puget Sound

At decadal period (10-20 years), dynamic linkage was evident between atmospheric low pressure systems over the North Pacific Ocean and circulation in a Pacific Northwest fjord (Puget Sound). As the Aleutian low pressure center shifts, storms arriving from the North Pacific Ocean deposit varying amounts of precipitation in the mountains draining into the estuarine system; in turn, the fluctuating addition of fresh water changes the density distribution near the fjord basin entrance sill, thereby constraining the fjord's vertical velocity structure. This linkage was examined using time series of 21 environmental parameters from 1899 to 1987. Covariation in the time series was evident because of the strong decadal cycles compared with long-term averages, interannual variability, and seasonal cycles.