Study ID 123

Maine Department of Marine Resources Inshore Trawl Survey 2000-2009 (OBIS-USA)

Download dataset

Realm: Marine
Climate: Temperate
Biome: Temperate shelf and seas ecoregions
Central latitude: 43.891199
Central longitude: -68.940737
Duration: 10 years, from 2000 to 2009

36935 records

144 distinct species

Across the time series Alosa pseudoharengus is the most frequently occurring species

Citation(s):

Sherman, S. (2010) "Maine Department of Marine Resources Inshore Trawl Survey, 2000 – 2009". Maine Department of Marine Resources, Maine. Available at: http://www.usgs.gov/obis-usa/data_search_and_access/datasets.html, accessed 2012.

Methods

DESIGNThe Maine-New Hampshire Inshore Trawl Survey is a stratified random survey with afixed component. The inshore area sampled includes four1 depth strata: 5-20 fathoms.21-35 fathoms. 36-55 fathoms. and >56 fathoms out to approximately the 12-mile limit.and five longitudinal regions based on oceanographic. geologic. and biological features(Figure 1). Together. 20 separate strata exist.With the addition of the fourth strata. the total survey area increased from ~3.626 nauticalmiles (NM2) to ~4.665 NM2. To keep sampling density of the original strata roughlyequivalent with previous surveys. an additional 15 stations were added to the originalgoal of 100 stations per survey. A target of 115 stations is selected for sampling in eachsurvey resulting in a sampling density of 1 station for every 40 NM2. Number of towsper stratum is apportioned according to its total area (Tables 1 and 2).SELECTION OF RANDOM STATIONSRandom stations are selected from a NOAA nautical chart in Arc ViewTM GIS overlainwith 1-NM2 grids. Each grid within each region is assigned a unique identificationnumber that serves as a call number. Grids are selected using an ExcelTM random numbergenerator. Tows approximately 1 NM long are proposed in each grid and plotted in PSeaWindplotTM (using charts of the NAD 1983 datum). From prior experience and localknowledge. some grids are classified as untowable during the plotting process. Due tothe large amount of fixed gear and the appeal to fishermen to cooperate with the surveyby clearing the tows. identifying good tow locations is a priority. If no towable bottomcan be found within a 2-mile radius. a new random number is chosen within the samestratum. Beginning and end points of each tow are identified in P-Sea Windplot. To theextent possible. for ease of identification by lobster industry members. tows follow loranlines. Loran C coordinates are converted to latitude/longitude degrees to the nearest0.001 decimal minutes.2SELECTION OF FIXED STATIONSAfter the initial survey in the fall of 2000. two stations per stratum were designated asfixed stations to be sampled on each subsequent survey. In areas where previous workhad been done. the stations were selected due to their historical importance3. In areas withno history. one station was selected as being roughly representative of the average catchfor its respective stratum and the other was randomly selected. After the addition of thefourth stratum in the spring of 2003. fixed stations were designated for that stratum usingthe same criteria.FISHING GEARTrawl design considerations for the survey include effectiveness of the gear forsampling the complex bottom in the nearshore areas of the Gulf of Maine andcomparability with previous and ongoing surveys by NMFS and MassachusettsDivision of Marine Fisheries. The net is a modified version of the shrimp netdesign used in Maine waters (Appendix A). designed to fish for a variety of nearbottomdwelling species without targeting any specific component. RobertTetrault. the vessels? owner. and net designer Jeff Flagg designed the net to fishfeet in length with nominal horsepower. Three identical nets were constructed forthis survey in the event of tearing or loss. Net tapers were cut to permit the shapeof the net to get maximum height while allowing the net to remain tight on thebottom. The net is shackled from the footrope to the frame with two 3/8th inchshackles to a banded wire that runs parallel with the footrope. Heavy rubber wingbobbins retard bottom wing lift at the net end of the bottom leg. Top legs are7/16th wire. 60 feet in length with soft eyes at each end. and bottom legs are 5/8thinch wire. 58 feet in length with two feet of 5/8th inch chain at the end where theleg attaches to the bottom wing for a total of 60 feet. Bottom legs are coveredwith 2 -3/8? cookies to prevent them from digging into the mud. The net isconstructed of 2-inch #24 polyethylene mesh. with a 1-inch (stretched measure)mesh liner in the cod end. Otter boards are #7.5 Bisons. Attached to the 70-foot.5/8th inch Rander?s Combination Wire Rope footrope is a roller frame strung onto?? IPS of 6x19 construction with a fiber core. The ten-foot wide bosom section ismade up of eight-inch rubber discs on six-inch centers along with eight evenlyspaced toggles. Spacing is maintained by smaller four-inch cookies strungbetween the discs. The two 29-foot wing sections are made up of six-inch rubberdiscs spaced 4 ? inches apart. with the same four inch cookies used to maintainspacing. Each wing section contains twelve toggles spaced evenly to facilitatefootrope attachment. The 5/8? Rander?s combination rope headrope has twentyeight8? center-hole. deep-sea net floats strung with 5/8? yellow polyethylenefloat line. Between surveys. the net is sent back to the manufacturer where it isreturned to specification (Appendix B). Nets will be replaced as they age to keepthe gear in good working condition and insure consistency. Unit of abundance = IndCountInt, Unit of biomass = Weight