Chartered vessels:

F/V Sea Eagle (Cruise 98-1)

F/V Pacific Sun IV (Cruise 98-2)

F/V Blue Horizon (Cruise 98-3)

F/V Amy Lynn (Cruise 98-4)

The Fisheries Resource Analysis and Monitoring (FRAM) Division of the Northwest Fisheries Science Center (NWFSC) recently completed its first deep water slope (100-700 fathoms) bottom trawl survey of the West Coast using local fishing vessels. This report summarizes the preliminary results from this survey.

The survey was conducted on board the chartered commercial trawlers Sea Eagle and Pacific Sun IV from August 15 through September 16, 1998 and the Blue Horizon and Amy Lynn from September 22 until October 21, 1998 (Table 1). These vessels began the cruise at Cape Flattery, Washington (48° 10’) and worked southward to Point Conception, California (35° 00’) sampling in predetermined areas and depths.

Groundfish slope surveys are designed to provide information on distribution, abundance and other biological resource information to assess the status of important fish stocks. During 1984-1997 the Alaska Fisheries Science Center (AFSC) Resource and Conservation Engineering (RACE) division conducted similar surveys from the NOAA ship Miller Freeman. The Miller Freeman was not available in 1998. The new survey effort from chartered vessels was designed as a pilot study to obtain similar data, although not technically equivalent. Specific objectives of the 1998 survey included:

1. Define the distribution and relative abundance of commercially important groundfish species particularly Dover sole (Microstomus pacificus), sablefish (Anoplopoma fimbria), longspine thornyhead (Sebastolobus altivelis), and shortspine thornyhead (S. alascanus) inhabiting depths from 100 fm to 700 fm.

2. Obtain biological data from groundfish species including length, weight, and sex.

3. Collect age structures from Dover sole, sablefish, longspine thornyhead, and shortspine thornyhead.

4. Quantify sampling effort by recording accurate net mensuration data on sampled hauls during the survey.

5. Compile other physical data (e.g. water temp) associated with groundfish abundance.

6. Collect special project samples or information.

The four vessels used in the charter ranged in length from 68-91 feet (LOA) with vessel horsepower ranging from 425-675 hp. An experienced captain and two crew members staffed each vessel. Two scientists staffed each vessel except the Sea Eagle which could carry three.

FRAM division provided standardized fishing gear for the survey. Each vessel used an "Aberdeen" style four panel bottom trawl with a small-mesh (2" stretched measure or less) liner in the codend in order to retain small organisms. The Aberdeen trawls were fitted with 8" and 10" rubber disc footropes and spread with 1200 lb. 5’ x 7’ steel Vee-doors. A Simrad ITI trawl instrumentation system was employed on each haul to monitor trawl performance and ensure that the gear’s haul-to-haul catching performance (sampling efficiency) was kept as constant as possible.

Sea surface temperatures were measured by using a bucket thermometer on three vessels. On the Pacific Sun IV a hull mounted thermometer was used and it proved more convenient and was as accurate as the bucket thermometer method. Sensors were placed on the trawl’s headrope to record bottom temperature profiles.

The West Coast slope survey was designed primarily to assess the distribution and abundance of a wide range of commercially important finfish species. The 1998 survey using local vessels was a combination of both systematic and random sampling strategies. Survey sampling locations were arranged along east-west transects with transects separated by 10 minutes of latitude. In total, there were 80 such transects covering the coast between the survey endpoints. At each transect, a total of 5 stations were selected from 2 categories: shallow (100-300 fms) and deep (300-700 fms). The stratum with the greatest linear distance was assigned 3 randomly selected depth ranges for sampling, while the category with least linear distance was assigned 2 randomly selected depths for sampling.

Each of the four vessels occupied a different subset of 20 transects separated by 40 minutes of latitude such that by the end of the survey all 80 transects had been sampled. Vessels started operation approximately at Cape Flattery, Washington and progressed southward down the coast completing the survey in Morro Bay, California.

The duration of each haul was approximately 15 minutes long from the time the net was properly configured on the bottom until haul back. Captains were instructed to attempt to maintain a constant speed from 2.0 to 2.2 knots. Bottom contact sensors, placed on the footrope of the net, verified that the trawl was on the bottom and monitored the duration of the tow. Acoustic instruments attached to the net recorded various aspects of their mechanical performance while other data on operational conditions (e.g. depth, amount of towing cable deployed, towing speed, tow duration, and weather conditions) were recorded on deck.

Catches were sorted to species or other appropriate taxon, then weighed. Samples were taken of the principal species for length-frequency determinations or acquisition of other biological data, using an electronic measuring board to log data. Following this, marketable fish were placed in the hold of the vessel, iced and delivered to a shoreside processing facility within 5 days. Such fish were part of the vessel’s compensation. All prohibited species and other marine organisms with no commercial value were returned to the sea.

A total of 319 stations out of 400 were successfully sampled (Table 2). Twenty-four stations were not occupied due to untrawlable bottom, telephone cables, or submarine lanes. Fifty-six stations were not attempted primarily due to bad weather or logistic constraints. Figure 1 identifies precisely where successful and unsuccessful sampling occurred.

Biological information was gathered from 32 different fish species. Table 3 illustrates the actual number by species of the approximately 65,000 total fish lengths and 3,609 total otoliths collected. The age structures will be examined and ages determined for these species at the Newport NMFS facility.

The fifteen most prevalent species cruise-wide are listed in Table 4. Species catch units (kgs/haul) are aggregated by International North Pacific Fishery Commission (INPFC) area and primary depth statum of 100-300 fathoms and 301-700 fathoms on a haul by haul basis. In this report, no adjustments have been made in catch rates for variations in bottom time, but we will be evaluating this variable in the next phase of analysis.

Figure 2 is a coast wide summary of fish lengths of 9 commercially important species. Figure 3 identifies the length of the 4 primary species, Dover sole, longspine thornyhead, shortspine thornyhead and sablefish, by INPFC area . Figure 4 and Figure 5 further illustrate the different length frequencies by sex of sablefish and Dover sole.