draft
date March 22, 1996
Construction Zone!!
Fishing Gear and Hook Removal Techniques used in the Longline Fisheries in Alaskan Waters; a Discussion Paper
by
This paper is presented as a review of the gear, terminology,
and hook removal techniques used in the longline fisheries in Alaskan waters.
In longline fishing, a vessel lays out a long line ('longline') which is
anchored to the bottom at each end, those ends marked with buoys and floats,
and with numerous hooks attached to this longline at some regular interval.
I recommend our Technical Report No. 22 The Pacific halibut: Biology, fishery
& management, as a valuable resource for anyone needing a refresher
on the basics of the longline fisheries. Although this report is particular
for halibut, the principles of longlining are the same in the Pacific cod
and Sablefish (blackcod) fisheries. Figures 1 and 2 are reproductions from
this report.
One area where there can be substantial confusion
is in trying to define the units of effort which are set out. In the later
1800's and into the middle of this century, all longline fishing off our
coast was conducted from small one or two man boats which were launched
daily by a mothership. These small boats would set out a half-mile or so
of longline and then, after a suitable 'soaking' time, retrieve it by hand.
Fish would be brought into the boat with the aid of a steel or iron hook
("gaff" or "gaff hook"). When the small boats were loaded or at the end
of the day, the men would return to the mothership where the fish were
cleaned (guts and blood removed) and the gear would be repaired and baited
for the following day's fishing). With the advent of powered hauling systems,
a multitude of techniques have developed for the setting and retrieving
of the longline gear. Although the basic fishing process is the same once
the longline is lying on the bottom, the different methods of setting and
retrieving the gear have required some basic differences in the hook types,
method of attachment of the gangions to the longline, and in the type of
equipment associated with both setting and hauling the gear.
As a very broad generalization, the major differences
between halibut and cod or blackcod gear are as follows: halibut is generally
fished with 'heavy' gear, consisting of strong, large diameter, long (30
inches or so) gangions and large size hooks with the hooks attached to
the groundline at wide intervals from as little as 3 to 4 feet to as much
as 18 or 20 feet with an interval of 9 to 12 feet being common; cod and
blackcod are generally fished with 'lighter gear', shorter and weaker gangions,
smaller hooks, and with a spacing between hooks in the neighborhood of
32 inches.
Conventional (fixed-hook) or skate-bottom gear:
This gear appears little changed from the gear used by the dory fishermen.
The hooks are tied to gangions which are tied to the small loops ("beckets")
fixed to the groundline (thus "fixed hook" gear), usually at a very regular
spacing. Longline material (groundline) is sold in spools which measure
1800 feet overall. This length is known as a 'skate' or 'skate of gear'.
In the dory days, groundline was sold in 300 foot sections. As groundline
became more commonly sold in 1800 foot lengths, it was traditional to remove
1/6 of this length (300 feet) to be used as a buoy line between the anchor
at the end of the longline and the buoy. This is still done by some vessels,
and it is therefore necessary when determining the amount of gear set or
hauled to record the length of each skate. Some vessels refer to an uncut
skate as a '6-line skate', (having six 300 foot sections), while a skate
where a buoy line portion has been removed is referred to as a '5-line
skate' (being 1500 feet in length, as in five 300-foot sections). During
setting, a buoyed anchor is attached to the end of one skate and the gear
is pulled off the stern as the vessel steams away. A 'chute' on the stern
is used to guide the gear off the stern. Additional skates are tied into
the end of the preceding skate and, when the vessel determines that enough
gear has been set, a buoyed anchor is tied to the end of the last skate
in the sequence. The gear is retrieved over a large horizontal "roller"
attached to the vessel's railing. Two smaller vertical rollers ("horns"),
one at each end of this larger roller, keep the groundline from slipping
either forward or aft of the large roller. Pulling power for gear retrieval
is achieved by a hydraulic line hauler, or sheave mounted amidships directly
inboard of the roller. These line haulers are quite strong and can typically
exert a pull on the order of thousands of pounds. Once through the hauler,
the gear is coiled onto a square piece of tarp (a "skate bottom"). As each
skate is brought aboard, it is untied from the skate still being hauled
and can then be tied into a bundle and set aside, or repaired and re-baited.
A conventional gear vessel is easily recognized by the presence of a chute
on the stern, a hydraulic line hauler ("sheave" or "gurdy") amidships,
and by the presence of tied up bundles of groundline (skates), usually
stored in a bin on deck.
Conventional gear is popular in the Gulf of Alaska fisheries
for Sablefish and somewhat for Pacific cod in this area. A major operative
difference between this gear for halibut and cod fisheries is in the length
of groundline which is coiled into each skate bottom. A typical halibut
skate would be 1800 feet long with between 85 and 150 hooks attached at
regular intervals. Because of the much shorter spacing between hooks, it
is common to have blackcod skates consist of a 900 foot length of groundline
with around 225 or more hooks fixed at regular intervals.
Tub-gear: A recent variation on the conventional fixed-hook gear is "tub gear", the major difference being that the gear is both set out of and coiled back into large plastic tubs rather than skate bottoms. The setting and hauling equipment is the same as that seen with conventional gear. Tub gear boats are distinguished by racks or stacks of tubs somewhere on the vessel's deck. The main operative difference between tub and conventional gear stems from the fact that you cannot coil an entire 1800' skate of gear into the tubs generally used. Generally, tub gear has 900 feet of groundline per tub. Also, because the gear is loosly flaked into the tub, gangions on tub gear tend to be shorter and of more flexible construction.Tub gear is popular in both the Pacific halibut and the cod/blackcod fisheries in the Gulf of Alaska.
Snap-on gear: This is a common gear on smaller halibut vessels (trollers, gillnetters and some seiners) and is uncommon on both larger boats or boats fishing for cod or blackcod. The groundline, usually in 1800 foot segments, is wound onto a large drum on deck. Originally, this drum was simply the gillnet drum on a gillnetter. As fishermen began carrying more gear and setting in deeper water, it became necessary to build special drums which were stronger and, sometimes, with a larger line capacity. As the gear is set, the individual gangions are fixed to the groundline by a snap which is attached at the end of the gangion away from the hook. The snap is a line grabbing type and can therefore be attached at any point on the groundline. Because of this, the spacing between hooks is variable and often a 'best guess' must be made of hook spacing. During gear retrieval, the longline is wound back onto the drum and the snap/gangion/hook component is disconnected at the rail as the gear is retrieved. Snap-gear boats are distinguished by a large drum of groundline and tubs, racks, or other containers on the deck where the snap/gangion/hooks are stored. Generally, snap gear is used only on vessels fishing for halibut.
Autoline gear: A number of large boats, particularly
those fishing for cod or blackcod, use autoline systems. In these, the
hooks and gangions are permanently fixed to the groundline as in conventional
gear. However, the gear is stored in racks, with the hooks topmost. The
groundline hangs in coils below the racks. The spacing between hooks is
fixed and as many as 1200 hooks will be on each rack. In this case, the
vessel usually counts effort in terms of the number of racks fished or
the number of hooks fished. These systems incorporate an automatic baiter
near the stern of the vessel. During retrieval, the system usually racks
each hook automatically. These systems are uncommon in the halibut fishery.
Studies
by IPHC have shown that most halibut are hooked in the left or right jaw
when caught on either autoline or conventional hooks. The halibut approaches
the bait, opening its mouth. Opercular action creates an indraft of water
into the mouth (water discharging through the open operculum), drawing
the bait and the hook into the mouth. As the fish swims away, the hook
is drawn against the side of the mouth, encircling the jaw.
As
the fish swims away, tension on the gangion draws the hook against the
jaw. The flesh (shown here as pink) around the jawbone (dark grey) compresses,
and, when tight, the gap (or 'gape') of the hook can actually open slightly.
This results in the hook 'snapping to' around the jawbone. In this position,
regardless of the direction from which the gangion is pulled, the hook
remains encircling the jawbone.
horning holding the gaff or some other bar
across the horns of the roller so that the fish is ripped off as the gear
is retrieved; essentially acting as a crucifier. Sometimes a fish is horned
by gaffing the fish in the head or body and holding it against the horn
as the gear is drawn by.
gangion cutting where the fish is released by cutting the gangion between the hook and the groundline, resulting in release with the hook still embedded in the fish.
hook stripper automated removal by allowing the fish to be torn from the hook as the groundline passes through a hook stripper. IPHC regulations define a "automated hook stripper" (commonly known as a crucifier) as a device through which the groundline can be passed during gear retrieval which allows the groundline and hooks to pass freely, but does not allow fish to pass, thereby removing fish from the hooks.
hook straightening where the gaff holds the hook against the roller until the hook is straightened, pulling out of the fish.
There are marked differences in hook removal injuries
between gear types, hook removal methods, and fish size. In general, injuries
are less severe for removals from lighter gear (autoline), by less severe
methods (cut gangions, hook straightening, and careful shaking), and for
larger fish. The least severe injury is a torn cheek wound, present in
over half of all fish removed by methods other than the hook stripper,
and predominant in fish carefully shaken from the hook. For fish removed
by the hook stripper, the most common injuries are a torn jaw and the more
severe torn cheek and jaw wounds. Halibut removed by the hook stripper
from conventional gear or heavier gear with larger hooks acquire more severe
injuries than those stripped from autoline gear, presumably due to the
softer nature of the autoline hook and its tendency to straighten as it
is pulled out. The least severe injuries are associated with careful shaking,
hook straightening, and gangion cutting, most of the fish removed with
these methods having wounds no more severe than a torn cheek.
Survival of discard Pacific
Halibut The IPHC has been conducting tagging studies directed toward
better understanding the survival of halibut discarded both by the directed
halibut fishery and by the cod and blackcod fisheries. A study conducted
in 1987 looked at the survival of halibut removed by crucifiers in the
halibut fishery. Halibut removed carefully from halibut gear are thought
to suffer a handling mortality on the order of three to five percent. Pacific
halibut removed by automated hook strippers suffer a handling mortality
which is as much as nine times that experienced by fish removed carefully
by the more traditional method of rolling the hook out of the mouth using
a gaff. This increased mortality results from more severe injuries in the
mouth area associated with the automated removal. As well, fish receiving
sublethal injuries as a result of this automated removal experience a significantly
reduced growth rate in subsequent years. A direct result of the 1987 study
was the banning of crucifiers in the halibut fisheries. In discussion this
ban, IPHC staff cautioned that horning fish would be worse than hook stripping,
although either would cause severe injuries. With the advent of the quota
fisheries for blackcod and halbut in Alaska, the IPHC is now allowing the
use of crucifiers to remove those fish which are intended for sale.
Ongoing studies and data needs We are currently
conducting a study into the injuries and mortalities associated with different
release methods from cod and blackcod style gear. A necessary part of our
process is the understanding of the makeup of the fleets involved, both
in the style of gears used and in the methods employed to remove halibut
from the hooks. This is where the NMFS observer program can be invaluable
to the IPHC. Their observations on gear types and halibut release methods
will allow us more properly define the problem, and thus focus our research
efforts where they are most needed.