Dataset: Northeast US Ichthyoplankton
Deployment: NEFSC-Bottom_Trawl

MARMAP used mainly a fixed station design covering the sample area of each survey approximately evenly (Sibunka and Silverman 1984, 1989).  EcoMon sampled the same spatial extent of the shelf as MARMAP, but used a random-stratified design based on the NEFSC bottom trawl survey design (Azarovitz 1981). The number of plankton strata (n = 47) is lower than the bottom trawl survey (n = 108) as the narrow inshore stratum and the offshore shelf-break stratum of the bottom trawl survey (Azarovitz 1981) are combined in the EcoMon plankton sampling design.  The area encompassed by each stratum determined the number of samples in that stratum.  The number of stations sampled during an EcoMon survey is approximately 30 % less than that of MARMAP.  Samples were collected four to eight times per year (primarily: January-February, March-April, May-June, July-August, September-October, and November-December) for each program (Richardson et al. 2010).

The basic station protocols were very similar for MARMAP and EcoMon (Jossi and Marak 1983, Ejsymont and Sherman 2000).  Samples were collected both day and night using a 61-cm bongo.  Net tow speed was approximately 1.5 knots. Double oblique tows were a minimum of 5-mintues in duration, and fished from the surface to within 5-m of the seabed or to a maximum depth of 200-m. The volume filtered of all collections was measured with mechanical flowmeters mounted across the mouth of each net. Mesh size of the net differed between the programs, and was 505-μm during MARMAP and 333-μm during EcoMon.  Samples were preserved in 5% formalin.

Processing of most samples was conducted at the Morski Instytut Rybacki in Szczecin, Poland; the remaining samples were processed at the NEFSC or the Atlantic Reference Center, St Andrews, Canada. Larvae were identified to the lowest possible taxon and enumerated for each sample. Plankton tows differ with respect to volume of water filtered and maximum tow depth. In order to make data values comparable, these values were normalized through the use of a standard haul factor: h = z * 10 / v, where z = maximum tow depth (in meters) and v = volume of water filtered (in meters cubed). Taxon abundance for each station was standardized to number under 10 • m-2 sea surface (Morse 1989).

References:
Azarovitz TR. 1981. A brief historical review of the Woods Hole Laboratory trawl survey time series. Canadian Special Publication of Fisheries and Aquatic Sciences. 58:62-7.

Ejsymont L, Sherman K. 2000. Poland and the United States' cooperation in fisheries ecology: a multidecadal retrospective. Bulletin Sea Fisheries Institute Gdynia. 3(3-10).

Jossi JW, Marak RR. 1983. MARMAP plankton survey manual. US Department of Commerce, NOAA Technical Memo. NMFS-F/NEC-21:258 p. URL: http://nefsc.noaa.gov/publications/tm/pdfs/tmfnec21.pdf

Morse W. 1989. Catchability, Growth, and Mortality of Larval Fishes. Fish Bul. 87(3):417-46. URL: http://fishbull.noaa.gov/873/morse.pdf

Richardson DE, Hare JA, Overholtz WJ, Johnson DL. Development of long-term larval indices for Atlantic herring (Clupea harengus) on the northeast US continental shelf. 2010. Ices Journal of Marine Science. 67(4):617-27. doi:10.1093/icesjms/fsp276

Sibunka JD, Silverman MJ. 1984. MARMAP surveys of the continental shelf from Cape Hatteras, North Carolina to Cape Sable, Nova Scotia (1977-1983). Atlas No. 1. Summary of operations. US Department of Commerce, NOAA Technical Memo. NMFS-F/NEC-33:306 p.

Sibunka JD, Silverman MJ. 1989. MARMAP surveys of the continental shelf from Cape Hatteras, North Carolina to Cape Sable, Nova Scotia (1984-87). Atlas No. 3. Summary of operations. US Department of Commerce, NOAA Technical Memo. NEFC-F/NEC-68:197 p.