NOTE Hernandez-Garcia: Diet of Xiphias gladius 



405 



lower wing length) and eye lens digestion ( measured 

 as decreasing lens diameter) were measured every 

 12 hours. Otolith digestion (measured as decrease of 

 the longest axis length) was measured at intervals 

 of 12 hours for blue whiting, although the third in- 

 terval was divided into two intervals (measuring each 

 6 hours). Otolith digestion was measured at inter- 

 vals of 2.5 or 1 hour for the chub mackerel. 



Results 



Stomach fullness analysis 



Data on fish length (SL), weight (W), and stomach 

 fullness (SF) from zones A and B are given in Table 

 1. Values of SF in zone A were higher than those in 

 zone B. In the latter area four stomachs were empty 

 whereas in zone A all stomachs had contents. 



nal column (as long as 78.5 cm). It was estimated 

 that otoliths and spines belonged to a total of 476 

 fish. Blue whiting, Micromesistius poutassou, was the 

 most important prey species by number (37.81%, 

 Table 3). 



Cephalopods were detected in 17.14% of the stom- 

 achs sampled, and the number of specimens was es- 

 timated as 26 (Table 2). They were always present 

 in those fish with the highest SF. The Omma- 

 strephidae was the most important family by num- 

 ber (35.6%) and Todarodes sagittatus was the pre- 

 dominant species (23.4%). The Histioteuthidae 

 ranked second in importance (21.4%) and Histio- 

 teuthis bonnellii was the dominant species (11.4%, 

 Table 4). 



Decapods of the order Natantia were found in the 

 stomach contents of two individuals (Table 2), and a 

 large specimen was identified as Acanthephyra 

 purpurea. 



Stomach contents analysis 



Zone A The swordfish diet consisted offish, cepha- 

 lopods, and decapods (Table 2). Fish were the most 

 important item by number (93.33%, Table 2), al- 

 though in 20% of the stomachs analyzed fish were 

 represented by only otoliths and bones. Atotal of 832 

 otoliths were collected. Most bone remains could not 

 be identified. Many of them consisted of a large spi- 



Zone B In zone B the swordfish diet consisted of 

 cephalopods and fish. Cephalopods represented the 

 most common food item in this area, revealing the 

 highest index of numerical importance (67.89%, Table 

 2). A group of six pairs of beaks and one free upper 

 beak with the same shape could not be assigned to 

 any family. These were called "Unknown A." A 

 description and sketches of this beak type (Fig. 2) 

 are given in the Appendix. Ommastrephidae was the 



Table 2 



Comparison of the dietary importance of the three major forage categories observed in swordfish stomachs from zones A (35 fish) 

 and B (21 fish). Data are given in terms of numerical frequency, frequency of occurrence, and index of numerical importance. 



