Data Sets, Monitoring: Auke Bay
Molly Sturdevant
Auke Bay Laboratories
Alaska Fisheries Science Center, NOAA Fisheries
Ted Stevens Marine Research Institute
17109 Pt Lena Loop Rd
Juneau AK 99801
(907) 789-6041
Molly.Sturdevant@noaa.gov
1. Plankton abundance
The MSI program at ABL was one of the initiators of a region-wide
program designed to monitor the temporal development of zooplankton
blooms in nearshore marine areas. This "Plankton Watch"
program developed with the growth of private-non-profit and state
operated hatcheries that released increasing number of salmon into
Alaska’s waters. The goal of this program has been to document
the species composition, abundance, and timing of potential prey
organisms as food for pink and chum salmon fry first entering nearshore
marine waters. This early marine residency of salmon fry is
crucial in determining survival to adult and year-class strength.
Plankton have been sampled yearly in Auke Bay since the 1970s as an
index of environmental conditions for salmon fry. The Auke Bay
Monitor station (ABM) is sampled weekly from March or April until fry
have left the nearshore habitat in June, then monthly, until October
each year. Three replicate samples of the upper water column are
collected with a 20-m vertical tow using a 0.5 m diameter, 243 Fm
mesh Norpac net. Settled volumes are measured immediately in the
laboratory, then samples are preserved for detailed microscopic analysis
of species, stage and size composition and enumeration. A
long-term database is maintained for interannual comparisons.
2. Water temperature and salinity
A 20-m temperature-salinity profile is measured with a CTD each time
plankton samples are collected. The hydrographic structure of the
surface water column used by juvenile salmon is thus monitored from its
spring structure of a freshwater lens over a colder, more saline
(denser) layer to a summer mixed structure throughout the period that
juvenile salmon use the nearshore and strait habitats.
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