Herring stock estimates from diving surveys of spawn for Georgia and Johnstone Straits in 1985 / by J.F. Schweigert and C.W. Haegele. : Fs97-4/1972E-PDF

"Using the results of spawn surveys, we estimated that 24,003 tonnes of herring spawned in Georgia Strait in 1985. The roe fishery removed another 6565 tonnes of potential spawners from Area 14. This yields a combined estimate of 30,568 tonnes for the prefishery spawner biomass in Georgia Strait. Of this total, 16,517 tonnes were estimated to have spawned in Area 14, mostly on Denman Island with minor spawnings on Hornby Island and along the Vancouver Island shoreline from Nile Creek to Qualicum Beach. In Area 15, 1614 tonnes were estimated to have spawned on Harwood and Savary islands and from Sliammon to Dinner Rock on the mainland shore. An estimated 5707 tonnes spawned in Area 17: 128 tonnes on Thetis Island and 5579 tonnes from north of Yellow Point south into Ladysmith Harbour. Another 165 tonnes were estimated to have spawned in Area 18. Only the early spawns in Johnstone Strait were surveyed by divers. Surface survey results were used to estimate the spawning biomass for the later spawns. The spawner biomass for Johnstone Strait was estimated at 1298 tonnes of which 1295 tonnes spawned in Area 12 and 3 tonnes spawned in Area 13. The total prefishery adult biomass for both Georgia and Johnstone straits was therefore estimated to be 31,866 tonnes in 1985. The spawns were in more shallow water and on more gently sloping beaches in Area 14 than in Area 17, although spawns were significantly wider in Area 14. Most of the spawn was deposited between 1 m above to 3 m below chart datum, and egg density declined with depth"--Abstract, page iv.

Lien permanent pour cette publication :
publications.gc.ca/pub?id=9.953339&sl=1

• Format MARC XML
• Format MARC HTML

Demander des formats alternatifs