migratory behavior and population distribution of the 

 offshore lobster population ranging from Corsair Can- 

 yon and the southeastern extremes of Georges Bank 

 to Baltimore Canyon off the coast of Virginia. A total 

 of 7,326 offshore lobsters were tagged and released at 

 52 localities, grouped into 29 composite release 

 stations to effect a logical pooling of release and recap- 

 ture information and expedite the plotting and 

 evaluation of the data. 



2. Cooper and Uzmann (1971) hypothesized, on the basis 

 of a described time-temperature relationship, that the 

 nature of the offshore lobster migration phenomenon 

 was a vernal shoalward movement to warmer water 

 with subsequent return to the outer edge of the shelf 

 and upper slope with the onset of fall and winter. In 

 this report we attempt to elicit qualitative and quan- 

 titative aspects of individual movements from 

 groupings of individuals referenced to release locality, 

 point of recapture, and time at large. 



3. Among the 945 recaptured lobsters, 584 (62%) were 

 reported by specific location, 183 (19%) by generalized 

 location, and 178 (19%) without location information 

 of any kind. A classification scheme is presented 

 which distinguishes between directed migrants and 

 those whose net movements over time are in- 

 consequential or not clearly directional. We have 

 defined a migrant as an individual that has moved a 

 distance of 10 miles or more in 10-120 days from time 

 of release to time of recapture. A total of 117 (20% of 

 584) lobsters meet our requirements of defined 

 migrants. 



4. Between 17 and 20% of the 576 recaptured lobsters 

 whose net movements were definable (classified 

 movements) demonstrated seasonal shoalward migra- 

 tion. The highly restrictive criteria used herein for 

 defining shoalward migrants have probably excluded 

 a considerable number of other recaptures that had, 

 in fact, migrated into shoaler water. Therefore, the es- 

 timate of 17-20% annual shoalward migration is 

 probably an underestimate. Approximately 25% of 

 the tagged population remained localized (non- 

 migrants) and some portion of the remaining 55-58% 

 of the classified movements (indeterminates) might, 

 through more definitive criteria of classification, be 

 assignable as shoalward migrants or nonmigrants. 



5. Forty-three (37%) of the defined migrants (117) mov- 

 ed laterally along the outer edge of the continental 

 shelf. There is no apparent reason for this lateral 

 movement easterly or westerly during spring and 

 summer. Discrete submarine canyon populations 

 seem unlikely in view of these lateral movements. In 

 contrast, 63% of the defined migrants moved into 

 shoal water. 



6. Analysis of the depth distribution of recaptured 

 lobsters by month of capture shows a pronounced 

 cyclical pattern of shoaling during March-August 

 followed by a return to the shelf margin and upper 

 slope during October-December. These cyclical 

 changes in depth by season, independent of net track 

 analyses, provides additional support for the 



hypothesis of Cooper and Uzmann (1971) of inshore- 

 offshore movements of the offshore lobster population. 

 7. The distribution of recaptured lobsters by month of 

 capture and mean bottom water temperature 

 demonstrates that the offshore lobster population, 

 through random and/or directed movements, main- 

 tains itself within a temperature regime of 8°-14°C. 



ACKNOWLEDGMENTS 



We thank National Marine Fisheries Service port 

 agents John V. Mahoney, Churchill T. Smith, Fred C. 

 Blossom, Paul P. Swain, and Dennis E. Main for in- 

 valuable assistance in locating, collecting, and reporting 

 tagged lobsters taken by the commercial fishing fleet. 

 Special thanks are due to John P. Laird, National 

 Marine Fisheries Service, Woods Hole, for assistance 

 with programming and execution of computer and 

 plotter runs. The laboratory draftsmen, John R. Lamont 

 and James A. Rollins, have our deep appreciation for 

 their patient craftsmanship with our many re- 

 quirements. Likewise, we sincerely thank Gwendolyn L. 

 Kelley, staff typist, and Gareth W. Coffin, staff 

 photographer, for their essential services in the final 

 production of this report. 



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Scotia to New Jersey. U.S. Dep. Commer., NOAA Tech. Rep. 



NMFS CIRC-376, 55 p. 

 COOPER, R. A. 



1970. Retention of marks and their effects on growth, behavior, and 

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COOPER, R. A., R. A. CLIFFORD, and C. O. NEWELL. 



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