CRUISE REPORT

Cruise No: W98-06B
FOCI Number: 3WE98
OSU Ship: WECOMA

Area of Operations:

Southeast Bering Sea and Gulf of Alaska

Itinerary:

Depart Dutch Harbor June 17
Arrive Kodiak June 30

Participating organizations:

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

Personnel:

CRUISE OBJECTIVES:

1) Recover a mooring that broke free from its anchor in the SE Bering Sea,

2) Survey the distribution of age-0 pollock in the western Gulf of Alaska for purposes of estimating abundance and mortality,

3) Collect samples of juvenile pollock for studies of growth, osteology, gear comparison (Methot versus Bongo nets) and the effects of preservation method on body shrinkage,

4) Collect samples of juvenile pollock prey using a modified Clarke-Bumpus net,

5) Occupy Line 8 in Shelikof Strait to maintain a time series of biological and physical sampling for El-Nino and NPZ special requests,

6) Ground-truth instrumented moorings located near Line 8 for El-Nino and NPZ special requests,

7) Sample in the exit region of Shelikof Strait to determine the effects of the 1997/1998 El Nino on the transport of fish into Shelikof Strait,

8) Collect information on nutrients, phytoplankton, and zooplankton (NPZ) to be used in mathematical models.

9) Collect age-0 pollock from an eddy to be used for growth and genetic studies.

Cruise Summary:

a) On 17 June, 11:00 ADT, we left Dutch Harbor and headed north into the Bering Sea toward the mooring M2 which had broke free. At station 1 (Table 1, Figure 1), the mooring buoy and all instruments, including the acoustic release, were recovered - all appeared to be in fine shape except the lowest CTD which had been dragged over the bottom and was badly damaged. Below the acoustic release was about 2 m of chain terminated with an intact shackle all else was lost. Except for the acoustic release, everything that was recovered was off-loaded in Kodiak and was stowed by Paul Anderson and Rich McIntosh of the NMFS Kodiak Lab. The acoustic release was kept aboard the Wecoma by Hugh Milburn for possible use during the next cruise.

b) Station 2 was sampled on 19 June, 1300 ADT, with the Methot net and this was the first of 96 Methot tows at 91 stations (Table 1 and 2). Four pre-planned stations were dropped because they were inaccessible. Excess time allowed twelve stations to be added giving a more even coverage of the area within the survey boundary (Figure 1). Although unplanned, pollock rough counts were taken and used to estimate the number of pollock per 10 m2 (Figure 2). When fewer than 70 of these fish were collected, those saved for otoliths (< 21) were measured to the nearest 0.5 mm using a ruler. The overall mean length of these fish (n=1049) was 24.2 mm SL, they ranged from 11 to 45 mm SL. Many of the pollock collected along the east coast of Kodiak Island (Stations 123 and 125) were noticeably large giving a relatively large mean size per haul but these fish were collected last (Table 3).

At seventeen stations (Table 1), the 60 cm bongo net (505 micron nets) was fished after the Methot net to verify that the Methot was not missing many small fish. Very few fish were collected in the bongo net and, although they were not measured, they appeared to be similar in size to those collected by the Methot. At ten other stations (Table 1), the large Clarke-Bumpus net was suspended in the mouth of the Methot net to collect potential prey of age-0 pollock. At three stations (Table 1), a second Methot tow was conducted to collect fish for osteological and shrinkage studies (Table 2). Sampling with the Methot at Station 75 (Table 1, Figure 1) was requested by Jeff Napp during the cruise to collect pollock in an eddy as indicated by a drifter. This sampling was restricted to approximately one hour (three good tows and one failure) due to low fish densities (11 fish/tow), shallow water (38 m) relative to the drogue depth (40 m), and time constraints. The fish (n=33) collected near this drifter were preserved in 95% ethanol for otolith and genetic studies. All of these net tows were oblique from near-bottom to the surface; however, the distance off-bottom was quite variable due to intermittent operation of the Scanmar electronics.
Surface temperature was measured several different ways. Coarse measurements were made with a bucket thermometer, incremented in whole degrees celsius, until it broke about midway through the cruise. Temperatures were recorded off the ship's flow-through system but they tended to be warmer than the bucket reading. A micro-bathythermograph (MBT) was attached to the Methot net. In addition to surface temperature, the MBT provided temperature profiles over the tow path at many stations. After one use, the MK7f temperature and light recorder was abandoned because the value of the data was judged insufficient to warrant the additional deck time needed to operate it. Records of the ship's flow-through system were saved on disk as were the ADCP data although this was not requested.

c) Beginning on 27 June at 20:24 ADT, we began the requested sampling for El-Nino and NPZ studies of Napp, Kendall, and Hinckley. This sampling was fully completed and involved CTD casts, bongo (20 and 60 cm), Tucker (1 m2), and CalVET net tows (Table 1, Figure 3). At some of the exit-region stations the bottom depth was >500 m so the Tucker net was fished only to 250 m. All of these deepwater stations were classified as second-priority sampling. The last of the exit region stations (Station 122) was surprisingly shallow (40 m), nevertheless, the requested operations were completed. During net tows, the Sea-Cat was used to indicate gear depth and the resultant temperature and salinity data were saved to disk.

APPENDICES

Table 1. Cruise Summary pg.1, 2, 3, 4, 5, 6
Table 2. Cruise Statistics
Table 3. Standard length of pollock preserved for otoliths. pg.1, 2
Figure 1. Plot of the mooring recovery station and all Methot stations.
Figure 2. Plot of the pollock catch (fish per 10 m2) from Methot grid samples.
Figure 3. Map of El-Nino and NPZ stations.