Food and Feeding Habits of Swordfish, 

 Xiphias gladius Linnaeus, in the Northwest Atlantic Ocean 



W.B. SCOTT 1 and S.N. TIBBO 2 



ABSTRACT 



Food and feeding habits of swordfish were studied by examining stomachs of 141 individuals captured 

 from July to October 1971 between the Grand Bank and the southeast part of Georges Bank in the 

 Northwest Atlantic Ocean. A wide variety offish species made up about 80% of the diet; the remainder was 

 squid. Species and size composition of food fishes depended on the feeding area. Large redftsh (Sebastes 

 marinus) were the most important food item in the Western Bank and Grand Bank areas, whereas silver 

 hake (Merluccius bilinearis) made the greatest contribution in the Georges Bank area. Barracud inas. family 

 Paralepididae, occurred most frequently and constituted about 20 percent of the fish diet for all areas. 

 Sabertoothed fishes, family Evermannellidae, also occurred in samples from all areas. 



The fact that swordfish are caught commercially 

 on baited hooks gives special significance to knowl- 

 edge of their food and feeding habits. 



Scott and Tibbo (1968) reported on stomach con- 

 tents of about 500 swordfish taken in the Northwest 

 Atlantic Ocean and noted that fish and squid (Illex 

 illecebrosus) constituted the principal food. Fish 

 outnumbered squid about 3:1 volumetrically. The 

 most important fish species were mackerel 

 (Scomber scombrus), white barracudina (Notolepis 

 rissoi), silver hake (Merluccius bilinearis), redfish 

 (Sebastes marinus), and the herring (Clupea haren- 

 gus). A total of 31 taxa (species and families) was 

 represented. 



In 1971, an additional 141 stomachs were analyzed 

 and, although the results were more or less in basic 

 agreement with the 1968 findings, sufficient devia- 

 tion occurred to warrant additional comments. The 

 1971 study also included analysis of musculature of 

 ingested species (fishes and squid) for mercury con- 

 tent, in an attempt to learn more about the source of 

 mercury in swordfish flesh. 



MATERIALS AND METHODS 



Study material consisted of 141 swordfish 

 stomachs collected during four cruises in the sum- 



mer and autumn of 1971 (Figure 1). All fish were 

 caught on longlines, using mackerel as bait. Stomach 

 contents were preserved at sea, and identifications 

 and volumetric analyses made later in the labora- 

 tory. Every effort was made to identify fishes to 

 species. Amounts offish and squid in stomachs were 

 measured separately, and then summed to provide a 

 figure of total volume of stomach contents for each 

 swordfish. 

 After identification, samples of all ingested 



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'Royal Ontario Museum. Toronto, Ontario, Canada. 

 2 Biological Station, St. Andrews, New Brunswick. Canada. 



Figure 1. — Map showing locations of 1971 swordfish 

 catches. 



138 



