. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LIFE AND PREY OF A NEMERTEAN 91 N = 136 89 124 74 67 38 96 71 53 35 61 20 140 144 88 23 21 9 16 24 40 1 I I Estimated total number / m2 --- Avg. number/m' all transects,at low tides /m in permanently marked areas, at low tides. May J J A S 0 N D J F M A M J J Aug Oct N D Mar Jun 1968 1969 1970 FIGURE 5. Mean densities (number/m2) of Paranemertes percgrina at Snug Harbor. A) shows fall recruitment of juveniles from eggs spawned the previous summer; B) major mortal- ity period of adults; and C) spring recruitment fr
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LIFE AND PREY OF A NEMERTEAN 91 N = 136 89 124 74 67 38 96 71 53 35 61 20 140 144 88 23 21 9 16 24 40 1 I I Estimated total number / m2 --- Avg. number/m' all transects,at low tides /m in permanently marked areas, at low tides. May J J A S 0 N D J F M A M J J Aug Oct N D Mar Jun 1968 1969 1970 FIGURE 5. Mean densities (number/m2) of Paranemertes percgrina at Snug Harbor. A) shows fall recruitment of juveniles from eggs spawned the previous summer; B) major mortal- ity period of adults; and C) spring recruitment from fall spawning. N is the number of 1 m2 quadrats in which Paranemertes numbers were counted. Vertical lines along dashed lines are ± one standard error from the mean. seen. At Snug Harbor, life history and densities are similar to those at Garrison Bay (Figs. 2, 5 ; Roe, 1971 ) but show more fluctuations. Prey densities Platyncrcls bicanaliculata. An annual, P. bicanaliculata, has highly synchronous spawning periods. A few spawned in June, especially at Garrison Bay ; but most of both the Snug Harbor and Garrison Bay populations spawned near August 1 in both 1968 and 1969, at which time there was almost a complete turn-over of each. Young specimens of P. bicanaliculata settle out of the plankton in about three weeks, 4 mm or less in length. They quickly grow to about 10 mm long, and over- winter at this size. In spring they grow to adult size (Figs. 6A, 7A; Roe, in prepa- ration ). Since P. bicanaliculata is the major prey organism of both mud flat P. percgrina populations, densities of this species were most carefully and frequently determined. Figures 6B and 7B show densities through time. There are not such strikingly linear decreases in numbers at Snug Harbor as at Garrison Bay. When samples were divided into those with and those without algae, trends showed that P. bi- canaliculata tends to be more abundant in algal covered areas than in bare mud,. Please note that thes
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
