Fisheries, Subsistence, and Habitat
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Search Again| Division: | Commercial Fish |
| Title: | Abundance, age, sex, and size statistics for Pacific herring in Lower Cook Inlet, 200-2003 |
| Author: | Otis, E. O. and J. L. Cope |
| Year: | 2004 |
| Report ID: | Alaska Department of Fish and Game, Regional Information Report No. 2A04-04, Anchorage |
| Abstract: | This report summarizes and archives abundance, age, sex, and size composition data collected from Pacific herring (Clupea pallasi) in the Kamishak Bay and Southern districts of Lower Cook Inlet during 2000-2003. In the Kamishak Bay District, aerial surveyors typically flew 13-16 surveys between 17 April-9 June to estimate the abundance and distribution of herring schools and milted shoreline. Inclement weather sometimes caused gaps in survey coverage and created turbid water conditions that compromised surveyors’ ability to see fish. Except in 2000, when only one vessel survey occurred, commercial seine vessels were chartered to collect early- and late-season herring samples to characterize the age, sex, and size composition of Kamishak Bay herring and index their abundance. Despite a complete closure of the commercial fishery, aerial surveyors documented a declining trend in biomass during 2000-2003. Surveyors observed 0.3-2.4 km (0.2-1.5 miles) of milted shoreline during 2000-2003, further evidence that Kamishak Bay herring are in low abundance. Over 15,000 Kamishak Bay herring were sampled for age, sex, and size during 2000-2003. Although recruitment was not sufficient to bring the Kamishak herring abundance back above the threshold for a commercial fishery, the 1996 and 1999-year classes stood out as being relatively strong. The age-4 cohort comprised over 46% of the herring sampled in 2003. Herring weights-at-age, which had been on a diminishing trend, appeared to stabilize by 2002 and increase slightly in 2003. Aerial surveyors typically flew four to eight surveys between 24 April-7 June to estimate the abundance and distribution of herring schools in the Southern District. Inclement weather did not typically affect survey conditions in the Southern District. Commercial seine vessels were chartered to collect herring samples in Kachemak Bay in 2000, 2001, and 2003. Similar to Kamishak Bay, aerial surveyors documented a generally declining trend of abundance in Kachemak Bay, estimating 6,500 tonnes (7,200 tons) in 2000 and 500 tonnes (600 tons) in 2003. Despite the relatively large biomass observed in 2000, surveyors did not observe any milted shoreline in Kachemak Bay during 2000-2003. However, the 2003 vessel survey documented active spawn on Glacier Spit on 9 May. Over 1,700 Kachemak Bay herring were sampled for age, sex, and size during 2000-2003. Similar to Kamishak Bay results, the 1999 cohort dominated the Kachemak Bay samples, with age-4 fish comprising over 60% of the herring sampled in 2003. |
| Keywords: | Abundance, age, Clupea pallasi, harvest, Kamishak Bay District, length, Lower Cook Inlet, Pacific herring, run biomass, sex, Southern District, weight |