Table 1. — Mean catch (ln(x + 1)/hour) 

 of gulf butterfish and number of trawls 

 sampled during each trip and lunar 

 phase. 



Trip 



Phase 



Number 



Mean 

 catch 



analysis of variance (ANOVA) model was devel- 

 oped to test for the effect of trip, lunar phase, and 

 the interaction between trip and lunar phase. 

 Scheffe's test was used to contrast each lunar 

 phase with the other three phases. 



Results 



Peak catch rate was observed to occur in the 

 first quarter moon phase following the new moon 

 (Fig. 1). There was a highly significant difference 



800 



700 



600 



among trips and lunar phases (Model 1, Table 2). 

 The interaction between trip and lunar phase was 

 not significant iP = 0.33) and was therefore 

 dropped from the model resulting in Model 2 

 (Table 3). In model 2, there was a highly signifi- 

 cant difference among trips and a significant dif- 

 ference among lunar phases. A comparison of 

 means using Scheffe's test for each moon phase 

 (Table 4) indicated that catch rate during the first 

 quarter moon phase was significantly greater 

 than catch rates during the last quarter, new, and 

 full moon phases. 



Table 2. — Analysis of variance table testing the 

 effects of moon phase (M), research trip (T), and 

 the interaction between trip and moon phase (T * 

 M) on gulf butterfish catch rates during three butter- 

 fish research surveys in the Gulf of Mexico 1984- 

 85. 



O) 



I 



o 



< 

 o 



z 

 < 



UJ 



500 



400 



300 



200 



100 



O O 



LUNAR DAY 



C 



■"Significant effect at P < 0.01 . 



Table 3. — Analysis of vanance table testing the 

 effects of moon phase (M) and research trip (T) on 

 gulf butterfish catch rates during three butterfish 

 research surveys in the Gulf of Mexico 1984-85. 



■"Significant effect at P < 0.01. 

 "Significant effect at P < 0.05. 



Table 4. — Mean catch rate per hour 

 (ln(x + 1)/hour) by lunar phase 



Lunar phase 



Catch rate/hour 



Figure 1. — Graph of mean catch (kg/hour I of gulf butterfish by 



lunar day. 



*P < 0.05. 



818 



