Family Corophiidae 



Corophium crassicorne Bruzelius, 1859. Arclic-Boreal 

 regions of North Atlantic and North Pacific; in western 

 Atlantic: Arctic south to Virginia, 0-200 m, gravel to silty 

 sand, tubedweller, filter-feeding detritivore (Bousfield 

 1973; Dickinson et ai. 1980). 



Perimeter of Georges Bank, 35-146 m, gravel and sand 

 bottoms, 8.3°-12.3°C. 

 Siphonoeceies smilhianus Rathbun, 1908. Western Atlan- 

 tic: Cape Cod south to Maryland, 10-90 m, sand bottoms, 

 tube-dwelling detritivore (Bousfield 1973; Dickinson et al. 

 1980). 

 Southwest Georges Bank, 66 m, sand bottom. 



Species Distribution Patterns 



None of the 97 species collected were ubiquitous over the 

 entire Georges Bank region, all of them were restricted in their 

 distribution to some degree. In comparing the spatial patterns of 

 gammarideans on the bank, it became apparent that many spe- 

 cies had similar patterns. One of si.\ patterns could be used to 

 characterize nearly all the species (Fig. 16). Although these pat- 

 terns are idealized and not followed exactly by each species, they 

 were useful in simplifying the data and in providing insights into 

 which environmental factors may be important in controlling 

 gammaridean distributions on Georges Bank. A discussion of 

 each of these patterns and the species described by it follows. 



Family Podoceridae 



Dyopedos arclicus (Murdoch, 1884). Boreo-Arctic regions 

 of North Atlantic and North Pacific; in western Atlantic: 

 Arctic south to Cape Cod; 10-75 m, filter feeder (Laubitz 

 1977). 



Northeast Peak of Georges Bank, 99 m, sand bottom, 

 8.9°C. 

 Dyopedos inonacaniha (Metzger, 1875). Boreal regions of 

 North Atlantic; in western Atlantic: Arctic south to Vir- 

 ginia; 20-300 m, gravel to silt-clay bottoms, filter feeder 

 (Laubitz 1977; Dickinson et al. 1980). 



Perimeter of Georges Bank, 35-187 m, sand and gravel 

 bottoms, 6.8°-11.3°C. 

 Dulichia tuberculata Boeck, 1870. Boreo-Arctic regions of 

 North Atlantic; in western Atlantic: Arctic south to Cape 

 Cod; 10-600 m, rock and gravel bottoms, filter feeder (Ste- 

 phensen 1935; Laubitz 1977). 



Northern Edge of Georges Bank, 156 m, sand bottom. 



Paradulichia typica Boeck, 1870. Arctic-Boreal regions of 



North Atlantic; in western Atlantic: Arctic south to Cape 



Cod; 60-1,100 m, silt-clay bottoms, filter feeder (Gurja- 



nova 1951; Laubitz 1977). 



Western Basin of Georges Bank, 157-187 m, sand and 

 silt -clay bottoms, 6.6°-6.8°C. 



DISCUSSION 



Zoogeography 



Georges Bank lies in the latitudes where the Boreal (cold-tem- 

 perate) and Virginian (warm-temperate) faunal provinces over- 

 lap (Bousfield 1973; Briggs 1974). In his study of the inshore 

 gammaridean fauna of the Cape Cod region, Bousfield (1973) 

 found the Virginian forms composed two-thirds of his species 

 list. In contrast, we found that two-thirds of the species on 

 Georges Bank were Boreal forms having their centers of distri- 

 bution in the cold waters north of Cape Cod. However, it should 

 be noted that the shallow central portions of the bank are chiefly 

 inhabited by Virginian species, and that nearly all the Boreal 

 forms are restricted to the perimeter of the bank. Therefore, our 

 results are in agreement with Bousfield's findings. 



Briggs (1974), in his discussion of the zoogeography of the 

 northwest Atlantic, summarized data for both fish and inverte- 

 brates which showed a clear trend for cold-temperate forms to 

 be amphi-Atlantic while most warm-temperate species are 

 endemic to the western Atlantic. The data presented in Bous- 

 field (1973), Dickinson et al. (1980), and this report indicate that 

 this distributional pattern is also true for gammarideans. 



Northeast Peak 



A group of six species (Table 1) showed a strong association 

 with gravel sediments and cold year-round temperatures (6°- 

 8°C) of the Northeast Peak. This group of species showed a 

 high fidelity to the Northeast Peak with only Anonyx sarsi 



Table 1. — Six pallerns of gammaridean distribution on Georges Bank. Species 

 in parentheses occurred in only one or two collections. 



Northeast Peak 

 Acanlhonotozonia serratum 

 A nonyx sarsi 

 (Dyopedos arclicus) 

 Gammaropsis maculalus 

 \felita sp. B 

 Neopleustes pulchellus 

 (Pardalisca cuspidala) 

 Tiron spiniferum 

 ( Tryphosella nanoides) 

 ( H'estwoodi/ta magalops) 



Perimeter 



Ampelisca macrocephah 

 Anonyx liljeborgi 

 Casco bigelowi 

 Corophium crassicorne 

 Dyopedos inonacantha 

 Ericihonius ruhricornis 

 Harptnia proptnqua 

 Hippomedon propinquus 

 Leptocheirus pinguis 

 Melita denlala 

 Orchomene pinguis 

 Photis denlala 

 Phoxocephalus holbolli 

 Pleusymies glaher 

 Podoceropsis niiida 

 Prolomedeta fasciala 

 Stenopleusles gracilis 



Western Basin 

 Ampelisca declivilatis 

 (Anonyx dehruyni) 

 Balhyniedon sausserei 

 {Byblis gaimardi) 

 (Dulichia tuberculata) 

 Epimeria loricata 

 (Eusirus cuspidatus) 

 Halice abyssi 

 Halirages fulvocinclus 

 Haliragoides inerniis 

 Haploops lubicola 

 Ischyrocerus megacheir 

 Melphidippa goesi 



Monoculopsis longicornis 

 Paradulichia lypica 

 Rhachotropis dtslincla 

 Slegocephalus inflatus 

 Ttnelonyx cicada 



Shoals 



Ampelisca vadorutn 

 Amphiporea giganlea 

 Pontogeneta inertnis 

 Psammonyx nobills 



Southern Edge 

 Ampelisca agassizi 

 Argissa hamatipes 

 (Eriopisa elongata) 

 (Gammarus annulatus) 

 Melita sp. A 

 Orchomene mlnula 

 Pleustes panoplus 

 Rhachotropis inflala 

 Rhachotropis oculata 

 Stenopleusles inerniis 

 (Synchelidium amerlcanum) 



Central 



A canthohuustorius intermedius 

 A canthohuustorius similis 

 A canthohuustorius splnosus 

 Acanthohaustortus sp. C. 

 Acanthohaustortus sp. D. 

 Bathyporeia quoddyensls 

 Sybils serrala 

 Hippomedon serralus 

 Monoculodes edwardsi 

 Parahaustorlus holmesl 

 Parahaustorliis longtmerus 

 Paraphoxus epislornus 

 Photis macrocoxa 

 Protohaustorlus deichmannae 

 Protohaustorius wigleyi 

 Pseudohaustorius borealis 

 Pseudunciola obliquua 

 Stenothoe minuta 

 Unclola Irrorata 



