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Cruise Number: MF98-06
FOCI Number: FOCI 4MF98
Ship: Miller Freeman

Area of Operations:

Gulf of Alaska


Depart: Dutch Harbor, 1 May 1998
Arrive: Kodiak, 10 May 1998

Participating Organizations:

Alaska Fisheries Science Center (AFSC)
Pacific Marine Environmental Laboratory (PMEL)

 Chief Scientist:  Affiliation
 Mike Canino  AFSC
 Participating Scientists  Affiliation
 Deborah Blood  AFSC
 Lisa Britt  AFSC
 Annette Brown  AFSC
 Elaina Jorgensen  AFSC
 Allen Macklin  AFSC
 Elizabeth Dobbins  AFSC
 Patrick O'Reilley  University of Washington

Objectives of Cruise:

The object of this cruise was to conduct studies on how hydrographic and/or atmospheric events affect the growth and survival of pollock larvae in Shelikof Strait. Eddies are common circulatory features generated in Shelikof Strait which may entrain pollock under optimal or sub-optimal conditions for growth. Sampling operations were planned within and outside of an eddy containing pollock larvae. Another process study was to examine the effects of storms upon the conditions for growth and survival by pollock larvae if one occurred during the cruise.

Summary of Operations:


ADCP Lines 0
ADCP backtrack "L" 0
CTD casts 49

Plankton tows
Bongos, 60 cm 77
Bongos, 20 cm 4

Fishing trawls
Tucker trawls 14
MOCNESS tows 5
Live tows 2
Methot trawls 0

Mooring deployment 0
Mooring recoveries 0
Satellite tracked buoy deployment 5
Loran-C drifters deployed 0
Loran-C drifters recovered 0

Samples Collected:
Chlorophyll samples 164
Nutrient samples 190
Microzooplankton samples 95
Plankton samples 95
Predator samples 0
Stomach samples 0
Pollock samples 0
Pollock larvae samples 1861
Pollock egg samples 0

Summary of Cruise:

The cruise began with an occupation of 48 stations located between FOCI grid lines 153 and 174 from 3-5 May, 1998. A total of 44 60 cm bongo net tows were conducted to determine the distribution and abundance of pollock larvae (Figure 1). Four satellite-tracked drifters were deployed, two of them in an area of high larval abundance, in order to detect circulation features in the sea valley. SeaCat CTD profiles from the bongo tows were contoured at 40 m depth, revealing significant structure within the sea valley and the intrusion of warmer, more saline water at the exit region of the sea valley (Figures 2 and 3)
The next phase of operations was occupation of 17 stations for the El Nino study, four of them at Line 8 and 13 in the sea valley and exit region of Shelikof Strait (Figure 4). Plankton sampling was conducted with 20 cm and 60 cm bongo nets and Tucker trawls (Table 1). Microzooplankton, chlorophyll, nutrients, and irradiance were sampled during 14 CTD casts taken at these stations.
The final phase of operations was a process study of an eddy in Shelikof Strait from 7-10 May. Satellite-tracked drifter trajectories indicated the presence of an eddy feature in the sea valley (no figure yet. PMEL can include one if they want to). A 28 x 48 km grid composed of 30 stations was chosen to be coincident with this feature. Twenty one stations were occupied for MOCNESS, Tucker, and 60 cm bongo tows (Figure 5). CTD casts were conducted at selected stations to profile water column structure and collect microzooplankton at stations in and out of the eddy. A storm event occurred on 8 May, suspending sampling operations for approximately 4 hours. Temperature profiles from CTD casts taken at the same station before and after the storm indicated an increase in the mixed layer depth (Figure 6). Sampling for post-storm effects was conducted at selected stations for the remainder of the cruise


Table 1. 4MF98 Cruise Summary of operations.
Table 2. 4MF98 Cruise Sampling summary statistics.
Figure 1. 4MF98 Bongo tow stations. Solid contours indicate larval abundance (individuals per 10 m2).
Figure 2. 4MF98 Temperature profiles from Bongo tow stations contoured on 40 m depth.
Figure 3. 4MF98 Salinity profiles from Bongo tow stations contoured on 40 m depth.
Figure 4. El Nino stations occupied during 4MF98.
Figure 5. Eddy stations occupied during 4MF98.
Figure 6. Temperature profiles from station F3 before and after storm event during eddy study.

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