210 
A comparison of catches of swordfish, 
Xiphias gladius, and other pelagic species from 
Canadian longline gear configured with alternating 
monofilament and multifilament nylon gangions 
Heath H. Stone 
Biological Station 
Fisheries and Oceans Canada 
531 Brandy Cove Road 
St. Andrews, New Brunswick, E5B 2L9 Canada 
E-mail address: stoneh@mar.dfo-mpo.gc.ca 
Langille K. Dixon 
P.O. Box 144 
Woods Harbour 
Nova Scotia BOW 2E0, Canada 
The Canadian large pelagic longline 
fishery extends from Georges Bank 
south of Nova Scotia to the Flemish 
Cap, east of Newfoundland, and oper- 
ates from May through November, 
when swordfish (Xiphias gladius), the 
main species targeted, migrate into 
and adjacent to the Canadian EEZ. 
Fishing effort progresses from west to 
east and back again and from offshore 
to inshore along the edge of the conti- 
nental shelf (Stone and Porter, 1999) 
following swordfish movements asso- 
ciated with seasonal warming trends 
of surface water temperature, and 
a northward movement of the edge 
of the Gulf Stream (Beckett, 1974). 
In winter, swordfish are confined to 
warmer waters associated with the 
Gulf Stream outside the Canadian EEZ 
and are not easily accessed by the Cana- 
dian fleet. In recent years, national 
swordfish quotas for the Canadian fish- 
ery (established by the International 
Commission for the Conservation of 
Atlantic Tunas) have been reached by 
early fall. 
Pelagic longlining was first intro- 
duced as a method for fishing swordfish 
in Canadian Atlantic waters in 1962, 
having been stimulated by reports of 
incidental swordfish catches by foreign 
longliners targeting tuna or laminid 
sharks (Beckett 1 ). Prior to 1962, har- 
pooning was the principal method used 
to capture swordfish on the continen- 
tal shelf, where large females (mean 
round weight -120 kg) were targeted 
as they swam or “basked” in surface 
waters during the day. This fishery oc- 
curred primarily during July and Au- 
gust, and required calm, clear weather 
to visually detect individual fish (Beck- 
ett 1 ). During the early to mid 1960s, 
the Canadian fleet rapidly converted 
to surface longline gear which proved 
to be far more efficient than harpoon- 
ing. Not only were daily catches much 
higher, but vessels could operate dur- 
ing inclement weather (unsuitable for 
harpooning) and fish farther offshore 
as waters cooled over the continental 
shelf. As a result, the fishing season 
extended, the fishing area expanded, 
catch rates increased, and the average 
weight of fish declined because both 
male and female swordfish were cap- 
tured (Caddy, 1976; Hurley and lies, 
1981; Beckett 1 ). 
Pelagic longline gear adopted for use 
by Canadian fishermen is similar to 
that used in the New England fishery 
(Berkeley et ah, 1981) and consists of 
a continuous backline up to 64 km 
long, supported in the water column 
by styrofoam floats with up to 2000 
baited hooks suspended on gangions 
spaced at regular intervals (Fig. 1). Al- 
though the general design of pelagic 
longline gear is relatively simple, op- 
erating characteristics (including area, 
month and time of set, surface temper- 
ature, fishing depth, number of hooks 
between floats, bait) can significantly 
affect the catch rates and species com- 
position of the catches. With swordfish 
fishing, usually three to five hooks are 
attached between floats and lightsticks 
are attached intermittently to some 
of the gangions above the bait to at- 
tract swordfish or their potential prey 
species. The gear is set during the ear- 
ly evening, allowed to soak overnight 
for 6-12 hours and retrieved at day- 
break. The length of the float lines de- 
termines the depth of the backline, and 
along with the length of the gangions, 
distance between buoys and speed at 
which the backline is set (i.e. the gear 
tends to sink more at slower setting 
speeds) determine the actual depth the 
baits will fish. In the Canadian sword- 
fish fishery, baits are often fished at 
depths of 12 m or less in the upper wa- 
ter column to take advantage of the di- 
urnal feeding migrations of swordfish 
and their movement into near surface 
waters at night (Carey and Robison, 
1981). 
In the early 1960s, the first floating 
longlines used modified halibut bottom 
longline gear buoyed by a variety of ob- 
jects (Beckett 1 ). Both the backline and 
gangions were made of tarred multi- 
filament nylon and the gangions were 
spliced directly to the backline. Mono- 
filament nylon was first used by Ca- 
nadian fishermen in the late 1960s, 
when a short (-38 cm) mono leader 
was attached between the tarred mul- 
tifilament nylon segment of the gan- 
gion and the hook. In the late 1970s 
(following an eight year closure of the 
Canadian fishery when it was illegal to 
land swordfish in Canadian ports ow- 
ing to perceived high levels of mercury 
in swordfish meat), gangions consisted 
of an upper tarred multifilament sec- 
tion with a clip for attaching it to the 
1 Beckett, J. S. 1971. Canadian sword- 
fish longline fishery. Int. Comm. Conserv. 
Atl. Tunas. SCRS Report 80/71/36, 14 p. 
International Commission for the Conser- 
vation of Atlantic Tunas, 8 Corazon de 
Maria, 28002 Madrid, Spain. 
Manuscript accepted 22 August 2000. 
Fish. Bull. 99:210-216 (2001). 
