Baum et al Bycatch of Hippocampus erectus in a Gulf of Mexico sfnrimp trawl fishery 



725 



In both years, there were significant differ- 

 ences in nonzero CPUE trawls among sites. 

 In 1998, CPUE was significantly higher in S2 

 than in 12, Nl, N2 and SI iFig. 3A, Table 1). In 

 1999. CPUE was significantly higher in area 

 Nl than in areas N3 and N4 IFig. 3B, Table 

 1). However, both of these spatial patterns, 

 like the lunar patterns, were driven primar- 

 ily by the high CPUE nights. Removing the 

 three outliers left a significant difference in 

 CPUE by area in 1998 only iTable 1). CPUE 

 did not vary with depth of the fishing ground 

 IP=0.67). 



Size of seahorses 



Mean standard length of adults (standard 

 length >105.3 mm) was 139.5 ±21.7 mm (n=465, 

 range 105.3-202 mm) and mean weight was 

 11.6 ±5.5 g (n=232, range 3-31 g). Hippocam- 

 pus erectus was sexually dimorphic: males had 

 a brood pouch and were significantly longer 

 than females (n=465, P<0.0005, Table 2), and 

 had a greater weight to standard length ratio, 

 although this latter difference was relatively 

 weak (P=0.04). Juveniles (standard length 

 <105.3 mm) had a mean standard length of 

 83.3 ±16.7 mm ln=65, range 41.4-105 mm) 

 and a mean weight of 2.4 ±1.0 g (?!=38, range 

 0.9-4.0 g). 



In adults, standard length varied by year 

 {n=425, F=l.\, P=0.008) and by lunar phase 

 (7!=425, cos(e):P=5.4, P=0.02, sin(0):P=7.7, 

 P=0.006). Mean standard length was greater 

 in 1998 than in 1999 and highest on the new 

 moon. In 1998 significantly larger adult sea- 

 horses were caught in areas 12 and S2 than 

 in II and SI (n=229, P=13.7, P<0.0005; Fig. 

 4). There was no effect of area in 1999 (n=2\2, 

 F=1.9, P=0.14). Standard length was not re- 

 lated to depth or tide. 



