14 



Fishery Bulletin 97(1), 1999 



depth for /. illecebrosus was 106 m, roughly 20 m 

 deeper than the average observed depth. Overall, L. 

 pealei was consistently associated with shallow 

 depths (37-75 m), whereas /. illecebrosus was more 

 common in deeper waters (79-149 m). 



The comparison of midranges for time of day indi- 

 cated whether L. pealei or /. illecebrosus catches were 

 more prevalent during night or day. We measured 

 time in relation to a reference time of day (6:00 AM 

 EST) because this roughly corresponds to first light, 

 during autumn, when diel effects on the behavior of 

 squid might be expected to change. This choice did 

 not affect the results of the habitat association test; 



however, median time of day was 18:00 EST, instead 

 of 12:00 noon EST. The midranges for time of day for 

 L. pealei and /. illecebrosus catches were 10:00-17:00 

 EST and 10:00-18:00 EST, respectively (Fig. 2B). In 

 comparison, the midrange for time of day was 13:00- 

 1:00 EST. For both L. pealei and /. illecebrosus, the 

 average median catch-weighted time of day was 14:00 

 EST, roughly 4 hours earlier than the average me- 

 dian time of 18:00 EST, and roughly equal to Pgg of 

 the overall time distribution. Overall, both L. pealei 

 and /. illecebrosus exhibited diel catchability because 

 squid catches were consistently greater during day 

 than at night. 



Potential effects of bottom temperature were also 

 examined to see whether L. pealei or I. illecebrosus 

 preferred warmer or cooler bottom temperatures. The 

 midranges of bottom temperature for L. pealei and 

 /. illecebrosus catches were 11-15°C and 9-13°C, re- 

 spectively, and the midrange for bottom temperature 

 was 8-13°C (Fig. 2C). For L. pealei, the average of 

 the median catch-weighted bottom temperature was 

 13°C, about 3°C warmer than the average of the over- 

 all bottom temperature distribution. For I. illece- 

 brosus, the average of the median catch-weighted 

 bottom temperature was 11°C, which was nearly 

 equal to the average of the observed bottom tempera- 

 ture distribution Although L. pealei was associated 

 with warmer bottom temperatures, it did not appear 

 that /. illecebrosus was closely associated with bot- 

 tom temperature. 



Effects of surface temperature were also examined 

 to see whether L. pealei or /. illecebrosus preferred 

 warmer or cooler surface temperatures. The mid- 

 ranges of surface temperature for L. pealei and /. 

 illecebrosus catches were 17-20°C and 13-20°C (Fig. 

 2D), respectively, and the midrange for all surface 

 temperatures was 11-19°C. For L. pealei, the aver- 

 age of the median catch-weighted surface tempera- 

 ture was 18°C; about 4°C warmer than the average 

 overall surface temperature distribution. Similarly, 

 the median catch-weighted surface temperature of 

 16°C for /. illecebrosus was 2°C warmer than this 

 average. Overall, L. pealei was generally associated 

 with warmer surface temperatures, whereas /. 

 illecebrosus associations were more variable, and this 

 species was less frequently associated with warmer 

 surface temperatures. 



Size-specific environmental effects 



Mean catches of L. pealei prerecruits and recruits 

 varied across depth zones (Fig. 3A) where combined 

 sample sizes for depth zones I, II, III, and IV were 

 1234, 1012, 270, and 99 tows, respectively. Mean 

 catches of prerecruits peaked in zone I and declined 



