1040 



Landers, Warren S. 1953. 



Spawning and setting of Venus mercenaries, in Wickford Harbor, 1950-1952. 

 4th Ann. Conf. on Clam Research, Boothbay Harbor, Me. U.S. Dept. Interior, 

 Fish Wildl. Serv.: 30-31. 



The Harbor has hard bottom along bars and points of land projecting into 

 the Harbor, and soft bottom in coves and in back of 2 large islands. 

 Currents are slow, maximum velocity about 1 knot in the main channel. 

 Salinity seldom varies. from 25 to 30 ppt. Spawning begins in late May or 

 early June, reaches a peak in June and decreases from then on. It may 

 continue at a fairly intense rate all summer, or virtually ceases about 

 mid-July. Temperature controls the beginning and length of spawning. It 

 usually ceases for all practical purposes by the end of September. Maximum 

 abundance of hard clam larvae during the 3 yrs was: straight hinge 8,000/35 

 gal, mature larvae ready to set 400 to 500/35 gal water. Density has been 

 low: 1950, 2.5/ft2; 1951, 1.8/ft2; and 1952, 1.5/ft 2 . - J.L.M. 



1041 



Landers, Warren S. 1954. 



Seasonal abundance of clam larvae in Rhode Island waters, 1950-52. U.S. Dept. 

 Interior, Bu. Comm. Fish., Spec. Sci. Rept.-Fish. 117, 29 p. 



Begins with a review of early life histories of My a arenaria and Venus 

 mercenaria, including descriptions of larvae. Venus begins to spawn in late 

 May or early June when water temp reaches about 2 0°C. Spawning continues for 

 the remainder of summer, usually decreasing in intensity until it ceases in 

 Sept. Isolated late umbone stages can occasionally be found well into winter. 

 In 1950 Venus larvae first appeared in the week of 11 June, in late May in 

 1951 and 1952. In 1950 spawning continued at relatively high levels until 

 nearly mid-Sept, but in 1951 and 1952 spawning was nearly completed by 

 mid-July. Water temp was consistently lower in 1950. There are some 

 indications that clams on shallow flats spawn earlier than those in deeper 

 water. Earliest shelled larvae ranged in length from 90 to 100 microns, 

 metamorphosing larvae to 225 microns. - J.L.M. 



1042 



Landers, Warren S. 1954. 



Notes on the predation of the hard clam, Venus meraenaria, by the mud crab, 

 Neopanope texana. Ecology 35(3): 422. 



Laboratory experiments showed that mud crabs will kill most hard clams 10 mm 

 long or less in aquaria, whether clams are buried in substrate or without 

 substrate. Clams 14 mm or longer were not touched. In a field experiment 

 hard clams 2 to 6 mm long were planted in fall and recovered in winter. 

 Only 258 of the original planting of 2,000 clams were recovered. It was 

 suspected, although not proven, that most mortality was caused by mud crab. 

 - J.L.M. 



1043 



Landers, Warren S. 1955. 



Summary of early life history studies of the hard clam in Rhode Island. 

 In 5th Conf. on clam research, Boothbay Har. , Me. U.S. Dept. Interior, 

 Fish Wildl. Serv.: 9-11. 



Spawning begins in both areas about the first of June and produces the most 

 abundant larvae. In hot summers spawning in Wickford Harbor is virtually 

 over by mid-July. Abundance of all stages of quahog larvae is usually greater 

 in Wickford Harbor than in Greenwich Bay, from 2 to 7 times as abundant in 

 early larvae and 2 to 11 times as abundant in mature larvae. Seasonal larval 

 mortalities ranged in Wickford Harbor from 95 to 97% and in Greenwich Bay from 



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