FOOD AND FEEDING HABITS OF JUVENILE ATLANTIC TOMCOD, 

 MICROGADUS TOMCOD, FROM HAVERSTRAW BAY, HUDSON RIVER 



Stephen A. Grabe* 



ABSTRACT 



Juvenile Atlantic tomcod from Haverstraw Bay (Hudson River, N.Y.) were found to have a May-June 

 diet of copepods and a July-December diet of amphipods, Neomysis americana, and isopods. This 

 dietary shift occurred when mean length reached 90 mm during July. Growth paralleled feeding 

 intensity: elevated during June, October, and November, and depressed July through September; 

 feeding intensity decreased prior to spawning (December). Feeding and growth were inhibited at 

 temperatures >24°C and dissolved oxygen <7mg/l. 



The Atlantic tomcod, Microgadus tomcod Wal- 

 baum, is an inshore marine fish whose range ex- 

 tends from southern Labrador (Bigelow and 

 Schroeder 1953) south to Virginia (Massman 

 1957); freshwater populations are localized in 

 Quebec and Newfoundland (Scott and Grossman 

 1973). The Hudson River may represent the 

 southern extent of the tomcod's breeding range 

 since it has not been reported from the Delaware 

 River estuary (de Sylva et al.^) and its status in 

 New Jersey waters is uncertain (Miller 1972; 

 Heintzelman^). In the Hudson River tomcod were 

 formerly considered to be a seasonal, migratory 

 species (Curran and Ries 1937; Clark and Smith"*); 

 more recent work, however, suggests that tomcod 

 remain in the estuary for their entire life cycle 

 (Lawler et al.^). 



Tomcod spawn as young-of-the-year and year- 

 lings (Lawler et al.^) with egg deposition typically 

 occurring during December and January ( Bigelow 

 and Schroeder 1953; Booth 1967). First year 

 growth, while initially rapid, slows in midsummer 

 (Howe 1971) and resumes in early fall (Lawler et 



'Lawler, Matusky and Skelly Engineers, Pearl River, N.Y.; 

 present address: 95 Ash Street, Piermont, NY 10968. 



Me Sylva, D. P., F. A. Kalber, and C. N. Schuster, Jr. 1962. 

 Fishes and ecological conditions in the shore zone of the Dela- 

 ware River estuary, with notes on other species collected in 

 deeper water. Del. Board Fish Game Comm., 164 p. 



^Heintzelman, D. S. (editor). 1971. Rare or endangered fish 

 and wildlife of New Jersey. N.J. State Mus. Sci. Notes 4, 23 p. 



*Clark, J. R., and S. E. Smith. 1969. Migratory fish of the 

 Hudson River. /n G. P. Howells and G. J. Lauer (editors), Hudson 

 River ecology, p. 293-319. N.Y. State Dep. Environ. Conserv. 



^Lawler, Matusky and Skelly Engineers. 1975. 1974 Hudson 

 River aquatic ecology studies. Bowline Point and Lovett 

 Generating Stations. Prepared for Orange and Rockland Util- 

 ities, Inc. 



^Lawler, Matusky and Skelly Engineers. 1976. Environmen- 

 tal impact assessment-water quaUty analysis: Hudson River. 

 National Comm. on Water Quality. NTIS PB-251099. 



al. see footnote 5; Texas Instruments^; Dew and 

 Hechts). 



Young-of-the-year Hudson River tomcod 

 undergo a dietary shift, from calanoid copepods to 

 Gammarus spp. amphipods, as they increase in 

 size (Texas Instruments see footnote 7). My objec- 

 tives were to define the diet and feeding intensity 

 of juvenile tomcod within the vicinity of Haver- 

 straw Bay, Hudson River, N.Y. 



MATERIALS AND METHODS 



Stomach contents of 577 juvenile tomcod were 

 analyzed as part of the postoperational biological 

 monitoring program for a fossil fuel steam electric 

 generating station located at Hudson River mile- 

 point 37.5. The study area (Figure 1 ) encompassed 

 Hudson River milepoints 37.5-41.5, as measured 

 from the Manhattan Battery. 



Tomcod were collected once monthly June- 

 December 1973 and 1974 by a 9.1-m otter trawl 

 with a 64-mm mesh cod end liner, towed against 

 the tide at 1.5-2.0 m/s. Collections of plankton and 

 juvenile fishes were made twice monthly June- 

 August 1974 with a 1-m diameter plankton net of 

 571-^tm mesh mounted in an epibenthic sled and 

 towed against the tide at 0.9-1.2 m/s. Tomcod from 

 May and December 1975 trawl collections were 

 also analyzed to provide a larger data base for 

 these months. 



Manuscript accepted June 1977. 



FISHERY BULLETIN: VOL. 76, NO. 1. 1978. 



'Texas Instruments, Inc. 1975. Hudson River ecological study 

 in the area of Indian Point: 1974 annual report (draft). Prep, for 

 Consolidated Edison Co. of N.Y. , Inc. 



*Dew, C. B., and J. H. Hecht. 1976. Ecology and population 

 dynamics of Atlantic tomcod (Microgadus tomcod) in the Hudson 

 River estuary. In Hudson River ecology. Hudson River Environ. 

 Soc., Inc. 



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