McEACHRAN and MUSICK: DISTRIBUTION AND RELATIVE ABUNDANCE OF SKATES 



Table 1. — Groundfish surveys conducted by the Biological 

 Laboratory of the National Marine Fisheries Service at Woods 

 Hole, Mass (now Northeast Fisheries Center). 



18 inch rollers on the ground rope was towed at 

 3.5 knots for 0.5 h at each station. Distance of 

 tow averaged 1.75 miles. 



Prior to data analysis, the 58 sampling strata 

 were grouped into five ecological subareas accord- 

 ing to hydrography and substratum. Schopf and 

 Colton (1966) stated that the southern Nova 

 Scotian shelf, Gulf of Maine, and Georges Bank 

 have different bottom temperatures and faunal 

 assemblages. Although Georges Bank and Nan- 

 tucket shoals (northern section of the mid- 

 Atlantic Bight) have similar bottom tempera- 

 tures and faunal assemblages (Schopf and Colton 



1966), the area extending from Georges Bank to 

 Cape Hatteras was subdivided because of its 

 great size. The southern section of the mid- 

 Atlantic Bight consisted of strata 61 to 76; the 

 northern mid-Atlantic Bight was composed of 

 strata 1 to 12 and 25; Georges Bank was made 

 up of strata 13 to 23; the Gulf of Maine included 

 strata 24, 26 to 30, and 36 to 40; and the Nova 

 Scotian shelf consisted of strata 31 to 35, 41, and 

 42. All four depth zones (27-55, 56-110, 111-183, 

 184-366 m) were sampled in the first three 

 subareas; the three deeper zones were surveyed 

 in the Gulf of Maine; and only two zones, 56-110 

 and 111-183 m, were sampled on the Nova 

 Scotian shelf. 



Preliminary examination of the skate data indi- 

 cated contagion as Taylor (1953) and Roessler 

 (1965) had demonstrated for trawl catch data in 

 general. A logarithmic transformation tends to 

 normalize contagious distributions (Pereyra et al. 

 1967), so skate counts were transformed to log 

 {X + 1). Transformed values were used to deter- 

 mine the geometric mean numbers (indices of 

 abundance) of skates per stratum per cruise. 

 The indices of abundance were weighted by 

 dividing them by the area of the strata to correct 



Figure 1. — Strata sampled by the RV Albatross IV and Delaware II, 1967-70. Strata numbers 43-60 were not included in 



the surveys. 



Ill 



