Table 1. — Longline cruises yielding swordfish for mercury analysis. 



Designation 



Date 



Number of 

 sets 



Area 



Number of 

 swordfish 

 sampled 



HS 104 



23-27 July 1971 



5 



Georges 



14 



DG 1 



23-31 Aug 1971 



8 



Banquereau and 

 Grand Banks 



63 



DG 2 



09-17 Sept 1971 



6 



Browns to Banquereau 



73 



DG 3 



14-27 Oct 1971 



6 



Georges to Cape Charles 43 



BIO 72-004 



01-22 Mar 1971 



8 



Bahamas and Caribbean 



17 



FG6 



27-May-8 June 1972 



12 



Cape Hatteras to Sable 



17 



FG7 



17-28 June 1972 



10 



Cape Hatteras and 

 Georges 



16 



FG 8 



6-19 July 1972 



14 



South of Browns to 

 Banquereau 



4 



FG 9 



26 July-9 Aug 1972 



13 



South of Grand Banks 



3 



FG 10 



14-31 Aug 1972 



10 



East of Grand Banks 



4 



Coryphaena hippurus; 1 long nose lancetfish, 

 Alepisaurusferox; 14 blue sharks, Prionace glauca; 

 4 sickle sharks, Carcharhinus falciformis; 1 dusky 

 shark, C. obscurus; 2 tiger sharks, Galeocerdo 

 cuvieri; 2 scalloped hammerhead sharks, Sphyrna 

 lewini; 2 mako sharks, Isurus oxyrinchus; 1 por- 

 beagle shark, Lamna nasus; and 4 unspecified 1am- 

 nid sharks). The size range of the organisms and total 

 mercury content of the dorsal muscle are shown in 

 Table 2. Similar data for a single white shark 

 (Carcharodon carcharias) obtained in an otter trawl, 

 and two basking sharks (Cetorhinus maximus) taken 

 from herring weirs in Passamaquoddy Bay, are also 

 included in Table 2. In addition, mercury determina- 

 tions were completed on 235 specimens of 1 2 species 

 of fish taken from swordfish stomachs (Table 3). 



DISCUSSION 



The areas of capture can be divided into five parts; 

 four divisions of the longline fishery and a fifth area 

 to the south; the latter includes the Bahamas and 

 eastern Caribbean. The captures in the northern di- 

 visions were made during four cruises in the period 

 July-October 1971. Captures from the southern area 

 were made in February and March 1972. The divi- 

 sions of the swordfish longline fishery are shown in 

 Figure 1 , while the dates of fishing are given in Table 

 1. 



Mercury levels found in swordfish tissue (dorsal 

 muscle) were tabulated (Table 4) by localities and 

 months. 



Variation With Size 



The slopes, correlation coefficients and "t" val- 

 ues obtained by application of the least squares fit 

 for linear relation between fork length (x) and mer- 

 cury content (y) are included in Table 4. It is appar- 

 ent that there is a relationship, although considera- 

 ble scatter exists. 



Table 2. — Total mercury level (ppm) of dorsal muscle 

 tissue of selected pelagic species. 



Species 



Number 

 sampled 



Fork length 

 (range) 



Total 



mercury 















Mean 



Range 







(cm) 



(ppm) 



(ppm) 



Swordfish 



210 



74-247 



1.15 



0.05-4.90 



Bluefin tuna 



1 



172 



0.80 



— 



White marlin 



1 



187 



1.34 



— 



Escolar 



1 



89 



0.62 



— 



Dolphin 



3 



88-115 



0.86 



0.32-1.22 



Lancet fish 



1 



122 



0.08 



— 



Blue shark 



14 



69-190 



0.70 



0.40-1.17 



Sickle shark 



4 



101-199 



1.43 



0.75-3.28 



Dusky shark 



1 



120.1 



2.08 



— 



Tiger shark 



2 



137-236 



0.83 



0.68-0.98 



Scalloped 











hammerhead 











shark 



2 



147-177 



3.64 



2.40-4.89 



Mako shark 



2 



151-159 



1.16 



1.02-1.30 



Porbeagle shark 



1 



116 



0.55 



— 



Mackerel shark 



4 



78-234 



2.08 



0.62-5.43 



White shark 



1 



449 



18.85 



— 



Basking shark 



2 



382 



0.08 



0.03-0.14 



155 



