Maine-New Hampshire Inshore Trawl Survey

The F/V Robert Michael, vessel used for the survey, is a Down East 54 constructed of a combination of solid and sandwich fiberglass and powered by an 8-cylinder 365 H.P GMC diesel. Reverse gear is a Twin Disc, Model 514, with a 4.5 to 1 ratio. A 3-inch stainless steel shaft turns a 47 x 45-inch, 4-bladed power propeller housed in a 48-inch Michigan nozzle. The vessel’s hull displacement is 73 gross tons, allowing it to perform well in sea states to eight feet.

The net used in this project is a modified version of a Maine shrimp trawl designed to fish effectively for a variety of benthic species; net tapers are cut to permit maximum height and tight bottom coverage. The footrope measures 70 feet with a roller frame of 6-inch rubber disks, a 10-foot bosom section with 8-inch disks, and a headrope of 59 feet. It has 2-inch stretched measure polyethylene mesh overall with a 1-inch stretched mesh liner in the cod end. The ground gear is comprised of 60-foot top legs and 60-foot cookie covered bottom legs. The doors are #7.5 Bison steel trawl doors. It is designed to be towed by vessels 45’ to 70’ in length with nominal horsepower. Nets are replaced as needed to keep the gear in good working condition and ensure consistency. A detailed manual of the net design was prepared by the Marine Institute at Memorial University, St. John’s, Newfoundland, Canada and is available upon request.

Selected finfish species may be examined for maturity, individual weight (in grams), diet analysis, and hard parts are collected for aging. The chief scientist determines what species and number of samples to process in each survey. When a maturity sample is processed, a sub-sample of ~25 individuals that consists of at least one fish per centimeter of lengths present is examined. All sexual maturity stages are determined as described in (Burnett et al., 1989). Otoliths are placed in a small envelope marked with the following information: Date, region, Tow ID, grid, fish length, weight (in grams), and sexual maturity. Otoliths are processed and aged back at the West Boothbay Harbor lab of Maine Department of Marine Resources.

All station data are recorded electronically in a data collection app and includes detailed information about each tow including, but not limited to, start and ending coordinates, times, depths, trawl wire deployed, weather conditions, and direction of the tow. Notes and comments on each tow are recorded in on the electronic app and in a logbook on the vessel to keep track of any additional information for each tow. All individual species/catch information is also recorded on data sheets. Additional sheets are used for sex, maturity, and stomach analysis data. Lobster data are recorded on voice recorders for later transcribing.

At the end of each survey, all data from each survey are entered and uploaded into the DMR’s Oracle database (MARVIN). Before uploading to MARVIN, all data undergoes data quality checks to assure accurate data is being uploaded for each survey. Tow locations are displayed in Arc MapTM, checked for accuracy, and adjusted as needed during the proofing stage. Data on the cruise forms for each tow is proofread by one of the scientific crew to identify and correct errors before data entry. Raw catch data (collected via trawl log or recorder) are entered into a Microsoft AccessTM database immediately following each cruise by the trawl survey scientists or additional DMR staff. Species are identified by the numeric code system used by the National Marine Fisheries Service. After entry, the data are proofread and edited again, then uploaded into DMR’s Oracle database. Environmental data is downloaded from the CTD into CNV files, converted into text files, and then uploaded into the Oracle database. The eSonar, Inc. data are cleaned of erroneous values and kept in Excel files. All final data are available to end users either by request or from viewing the data portal on Maine DMR’s website.