Koeller: Influence of temperature and effort changes on lobster catches 



67 



e.g. those that are southerly and enter directly into the 

 bays, and are of a minimum force, or both, one would 

 expect a positive correlation between water tempera- 

 tures and catches in these areas. The apparently spu- 

 rious correlation between lobster catches and tempera- 

 ture would be weaker in the exposed central area where 

 fishing activity is vulnerable to winds from a wider di- 

 rection and of less force than those which significantly 

 impact near-shore water temperatures. Although it is 

 clear that the observed correlations between short-term 

 changes in lobster catches and temperatures are 

 strongly influenced by changes in effort, these results 

 do not rule out a concurrent direct affect of tempera- 

 ture on lobster activity and catches, i.e. effect of 

 catchability. Possibly fishermen are aware that winds 

 of a certain direction and force affect lobster activity 

 and catchability and alter their fishing activity accord- 



ingly, or the factors that decrease fishing activity also 

 decrease lobster catchability independently. 



These results indicate that although changes in 

 effort can influence lobster catches at all spatial and 

 temporal scales examined, data on effort is particu- 

 larly critical in correctly interpretating the meaning 

 of changes in catch at smaller scales i.e. <100 km 

 and <1 yr. In particular, they indicate that small- 

 scale correlations between environmental param- 

 eters such as winds and water temperatures with lob- 

 ster catches alone should be treated cautiously because 

 inferences made about their underlying mechanisms 

 may be wTong. For example, Hudon (1994) concluded 

 that differences in annual catches between approxi- 

 mately 100-km lengths of the Nova Scotia coastline 

 were due to differences in the orientation of these coast- 

 lines to upwelling winds, the resultant change in wa- 



