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Fishery Bulletin 104(2) 



E 100 



ra 20 



00 (IN) 01 (IN) 02 (IN) 01 (OFF) 02 (OFF) 



Year (survey program) 



Figure 3 



The stratified mean carapace length (CL) for 

 American lobsters tHomarus amei'icaniis) for each 

 sampling season and year for the Maine Depart- 

 ment of Marine Resources inshore (IN I and the 

 National Marine Fisheries Service offshore (OFF) 

 survey programs. 00 = 2000; 01 = 2001; 02 = 2002. 



either fall or spring survey) for the inshore survey 

 (Fig. 4). For the NMFS survey, however, significant dif- 

 ferences were found in size distributions between 2001 

 and 2002 in the fall surveys, but not between the two 

 years in the spring surveys. The seasonal differences 

 (i.e., spring vs. fall) in size distribution within a year 

 were much larger than the between-year differences for 

 the inshore fall or spring survey. For the NMFS survey, 

 however, the seasonal differences in size distributions 

 were large in 2001, but small in 2002 (Fig. 4). The large 

 seasonal differences in a year compared to the between- 

 year differences in a season in size distributions for the 

 inshore survey indicate that seasonal factors are impor- 

 tant in determining the size distribution of lobsters in 

 the inshore waters. Such seasonal variability was not 

 so clear for the offshore waters. 



Large differences in size distributions were observed 

 between the DMR inshore and NMFS surveys; the 



NMFS surveys consisted of lobsters of much larger 

 sizes than those sampled inshore (Fig. 4). This finding 

 may indicate that the inshore survey program had a 

 limited coverage of the lobsters of large sizes, whereas 

 the NMFS survey program had a limited coverage of 

 the lobsters of small sizes. The size composition of lob- 

 sters from the NMFS survey had large variations. This 

 result was probably due to the small number of lobsters 

 caught in the NMFS survey. An increase in sample size 

 could make the size composition curve smoother, and 

 thus better defined. Compared with size composition of 

 Amercan lobsters from the NMFS survey, size composi- 

 tion for the inshore survey was better defined, probably 

 as a result of the larger number of lobsters caught in 

 the inshore survey. 



The stratified mean sizes of lobsters were similar 

 among years for the same sampling season in the in- 

 shore survey (Fig. 3). For 2001, the stratified mean size 

 in the fall survey was almost the same as that in the 

 spring survey. For 2002, however, the stratified mean 

 size in the fall survey was about 7 mm larger than that 

 in the spring survey (Fig. 3). The stratified mean size of 

 the 2001 fall survey was about 16 mm smaller than that 

 of the 2001 spring survey (Fig. 3). The stratified mean 

 size of lobsters in the NMFS survey was much larger 

 than that of the inshore survey. This reconfirms the re- 

 sults derived from the comparisons of size distributions 

 between the inshore and NMFS surveys (Fig. 4). 



The abundance index derived from the inshore survey 

 program revealed a consistent temporal pattern with 

 original data or retransformed data (Table 2). For the 

 original data and retransformed data, the fall inshore 

 survey abundance index was the highest in 2001, fol- 

 lowed closely by 2002, and the abundance index in 2000 

 was the lowest. For the log-transformed data, however, 

 the differences among the three years were small (Table 

 2). For the spring survey, the abundance index in 2002 

 was much higher than the abundance indices in 2001 

 and 2003, and the abundance indices in 2001 and 2003 

 were similar (Table 2). The delta mean abundance indi- 

 ces of the NMFS survey program were higher in 2002 



