aforementioned 0.9 mile (0.16.8 km) category. Accord- 

 ingly, we have adopted the premise that time or dis- 

 tance values under 10 preclude realistic interpretation of 

 directionality or speed of movement. 



Commercial fishing effort, monthly distribution 

 patterns of tagged recoveries (Figs. 34-45), and support- 

 ing details (appendix tables) all combine to show that 

 offshore lobsters are essentially aggregated along the out- 

 er edge and slope of the continental shelf during January 

 through April (120 days) and become widely dispersed by 

 migration or random movement in shoaler/warmer water 

 during May through December (245 days). We have set 

 the upper limit of duration of a directed migration at 120 

 days, or the theoretical half-life of a migratory season 

 during which the migrant can move to shoaler/warmer 

 water and return to the continental shelf margin in ap- 

 proximate phase with the annual shoalward and seaward 

 migration of the bottom temperature warm front (here 

 defined as the 10°C isotherm). Within these constraints 

 we regarded a total of 117 individuals as migrants; rank- 

 ing of these individuals by calculated ground speed 

 shows a range of 0.1-5.5 miles (0.18-10.2 km) per day, a 

 median speed of 0.9 miles (1.7 km) per day, and a median 

 at 0.6 miles (1.1 km) per day. Ground speeds of defined 

 migrants are positively correlated with distance travers- 

 ed and negatively correlated with time at large. 



The remainder of recaptures for which capture loca- 

 tion and time at large are known fall into three categories 

 of relative displacement from point of release. Our work- 

 ing definitions of migrant and alternative classifications 

 are as follows: 



a) Migrant by virtue of track >10 nautical miles (18.5 

 km) and time at large 10-120 days (N = 117). 



b) Nonmigrant by corollary definition of track < 10 

 miles and time at large < 10 days (N = 15). 



c) Residual nonmigrant by virtue of track< 10 miles, 

 time at large >10 days (range 15-950); this classification 

 reflects stationary behavior, or the alternative possibility 

 of undetectable excursion(s) with homing back to release 

 locality (i.e., within 10-mile radius of release point) (N 

 = 147). 



d) Indeterminate by virtue of track >10 miles (range 

 10-181), time at large>120 days (range 125-1,549); move- 

 ment is regarded as random dispersal, a summation of 

 migration tracks, or a combination of both (JV = 297). 



Eight recaptures were reported without dates of recap- 

 ture and hence could not be classified. These alternative 

 classifications make for interesting conjecture in many 

 cases; among the indeterminates, for example, we find 

 many probable examples of directed migration which 

 cannot be properly assessed because of the associated 

 element of excessive time at large; these cases will be 

 identified and discussed under the appropriate com- 

 posite station resumes which follow this section. 



Returning to the reliability of ground speed calculated 

 from D/T, we have assumed that D is probably un- 



derestimated in most cases because a lobster track of 

 significant distance over the bottom is unlikely to be 

 straight-line, and also because some of the recaptures 

 were likely on a return course relative to their original 

 shoalward vector. Conversely, T is probably 

 overestimated (but never underestimated) in a majority 

 of cases because the migrant under consideration had 1) 

 earlier arrived at destination, 2) had accumulative rest 

 periods, and/or 3) was on a return vector. The net effect 

 of any or all of these possible biases on calculated ground 

 speed is to underestimate the derivation in general and 

 to give added credence to values on the order of 4-5 miles 

 (7.4-9.3 km) per day. 



COMPOSITE STATION RESUMES 

 Composite Station 1 (See Appendix Table 1) 



Three recaptures have been reported from a composite 

 total of 42 releases in the vicinity of Oceanographer Can- 

 yon on 15 March 1968 (28), 16 March 1968 (5), and 30 

 March 1968 (9). Mean depth at first capture was 153 

 fathoms (280 m); mean depth at release was 175 fathoms 

 (320 m). Only one of the recoveries was reported by loca- 

 tion. The sex ratio of the three returns was one female to 

 two males. 



The most noteworthy feature of the recoveries from 

 this composite release is the relatively high mean time at 

 large (985 days =2.7 yT) which exceeds that of all other 

 subgroups of recoveries. The single located recovery, a 

 mature male, was captured 13 miles (24.1 km) from its 

 original release point and had been at large 1,342 days 

 (3.7 yr). 



Here, as in many other cases of lengthy time at large, 

 the relatively small displacement from original release 

 locality is indicative of either highly localized 

 movements over time or, alternatively, a homing tenden- 

 cy following larger scale movements. We prefer the latter 

 hypothesis and will attempt to sustain this view in the 

 remainder of the text on the basis of other individual and 

 collective returns. 



Composite Station 2 (See Figure 5 and 

 Appendix Table 2) 



Three recaptures, all males, have been reported from a 

 single point release of 13 lobsters near the head of Veatch 

 Canyon on 4 April 1968. First capture depth and release 

 depth were at 110 fathoms (201 m). Two of the recaptures 

 were reported by location with neither having migrated 

 very far nor having been at large very long. The third 

 recapture, a mature male, had been at large 741 days (2.0 

 yr), and was reported taken in the vicinity of Veatch Can- 

 yon without specific coordinates. 



This subgroup of recoveries represents the highest rate 

 of recapture (23%) among the 29 subgroups of releases 

 and indicates that numerically small releases of tagged 

 lobsters can yield significant returns. 



