Sea-Bottom Photographs and Macrobenthos Collections 

 from the Continental Shelf off Massachusetts 



By 



ROLAND L. WIGLEY and ROGER B. THEROUX, Fishery Biologists 



Bureau of Commercial Fisheries Biological Laboratory 

 Woods Hole, Massachusetts 02543 



ABSTRACT 



Epibenthic invertebrate animals were sampled with a large scallop dredge and 

 photographed with a sled- mounted camera at four locations on the Continental Shelf 

 off Massachusetts in August 1965. 



Sea-bottom photographs taken at a station south of Martha's Vineyard, Mass., 

 at a depth of 59 m. revealed a sandy silt sediment with a slightly uneven micro- 

 topography. At three stations on southeastern Georges Bank, at 64 to 82 m., sedi- 

 ments were predominantly sand with small proportions of shell fragments and silt. 

 The microtopography was generally rough and irregular, largely caused by feeding 

 of fish and other biological activity. Sand ripples were common; some apparently 

 formed by wave action and others by tidal currents. 



Species composition of the large epibenthic invertebrates was similar at the 

 three localities on Georges Bank but differed markedly from that south of Martha's 

 Vineyard. Also, the number of specimens were substantially higher on Georges 

 Bank than south of Martha's Vineyard. The densities of invertebrates estimated 

 from photographs (0.7, 1.7, 1.8, and 8.6 individuals per square meter) at the four 

 stations were substantially higher than estimates based on the dredge collections 

 (0.02, 0.16, 0.3, and 3.3 individuals per square meter). 



INTRODUCTION 



Undersea photography has proved exceed- 

 ingly useful in recent years for determining 

 geological features and biological components 

 (Ewing, Vine, and Worzel, 1946; Vevers, 1952; 

 Laughton, 1957; Thorndike, 1959; Mclntyre, 

 1956; Shipek, 1960; Menzies, Smith, and Emery, 

 1963; Barham, Ayer, and Boyce, 1967;Hersey, 

 1967; Wigley and Emery, 1967; and others). 

 Even in great oceanic depths of the bathyal 

 and abyssal zones, the animal life, bottom 

 sediments, and similar subjects have been 

 documented by photographs (Laughton, 1959; 

 Shipek, 1960). Of particular interest to us are 

 the studies that demonstrated the possibility 

 of using sea-bottom photographs to obtain 

 quantitative evaluations of epibenthic animals 

 (Mclntyre, 1956; Menzies, Smith, and Emery, 

 1963; Barham, Ayer, and Boyce, 1967; Wigley 

 and Emery, 1967). 



Because of the urgent need for more accurate 

 and economical methods of measuring the 

 density distribution of benthic animals, we took 

 a series of photographs at the same stations 

 where samples were collected with a dredge. 

 This report describes the photographic method 

 and presents the results, including a compari- 



son of the two methods of estimating densities 

 of the macrobenthic fauna. 



MATERIALS AND METHODS 



Sea-bottom photographs and dredge samples 

 were collected from aboard the research 

 vessel Albatross IV in August 1965 at four 

 stations on the Continental Shelf south and 

 southeast of Massachusetts at water depths 

 between 59 and 82 m. (table 1, fig. 1). At 

 each station a sample of benthic animals was 

 collected with a large scallop dredge and a 

 series of photographs was taken with an under- 

 water camera. 



Photographs were obtained with a camera 

 and light unit mounted on a heavy steel sled 

 (fig. 2) that was towed along the ocean bottom. 

 Basic features of the sled are generally 

 similar to Costeau's "Troika" (Gaston Fredj, 1 

 personal communication) and the submarine 

 plow developed by Bell Telephone Company 

 (Robert Allen, 2 personal communication). A 



""•Gaston Fredj, Biologist, Musee Oce'anographic, 

 Monaco. 



2 Robert Allen, Scientist, Bell Telephone Research 

 Laboratory, Chester, N.J. 



