8
J. E. SHELBOURNE
before the addition of milt. Fish caught on trawl-lines gave better
results than netted fish ; cold weather was more favourable than warm
for the subsequent transport of eggs to the home port.
Back in harbour, eggs were examined, cleaned, re-suspended in
offshore water and transferred to large glass jars wrapped in sacking.
Consignments travelled to the nearest hatchery by first train, accompanied by a messenger, whose task was to regulate water temperature
by frequent applications of snow or ice to the sacking. Fishing trip8
usually lasted 12-18 h ; if vessels were delayed by contrary winds or
tide, collected eggs were liberated into the sea over the spawning
grounds.
2. Spawn-taking from captive stock at Wo& Hole
The U.S. Fish Commission schooner " Grampus " and two or more
commercial smacks were employed on hand-line fishing for ripening
cod in 10-40 fathoms of water. Each vessel was fitted with a well for
housing captive fish during transport to the hatchery. There they were
transferred by dip-net to large, wooden, floating pounds, moored in
the middle of a wharf-protected basin. Casualties among ripening
stock were usually high-of the 1600 to 9000 fish held annually at
Woods Hole up to the year 1897, not more than 33% yielded eggs.
Dead fish were regularly removed from the pens, and fish ready to
spawn placed in a separate pound for the " stripping " operation.
The spawning of the female cod usually extends over 2 or 3 weeks ;
all oocytes do not mature and enter the oviduct at the same time.
Fish were therefore " stripped " at intervals of a few days until the
ovaries became completely discharged, the " spent " fish being returned
to the sea. About 80% of all eggs taken in a season were fertile.
3. Egg incubation
The Amerioans used two types of incubator for marine fish eggs;
the Chester jar, and the McDonald tidal hatching box. Both devices
incorporated the principle of sea water renewal with intermittent
siphon discharge, thus keeping the eggs in constant motion.
The Chester jar was an ordinary wide-mouthed glass container
about 23 cm diameter and usually 46 cm tall, with a central 12 m m
hole bored in the bottom, fitted with a plug. Roughly 200 000 egga
were introduced into the jar, in sea water, with the plug in position.
The mouth waa then covered with cheese-cloth or linen scrim held fast
by rubber bands, and the jar inverted, under water, to rest on supports
in wooden box fitted with a siphon. Sea water ran in at one end
of the box continuously, and out through the intermittent siphon at
J. E. SHELBOURNE
before the addition of milt. Fish caught on trawl-lines gave better
results than netted fish ; cold weather was more favourable than warm
for the subsequent transport of eggs to the home port.
Back in harbour, eggs were examined, cleaned, re-suspended in
offshore water and transferred to large glass jars wrapped in sacking.
Consignments travelled to the nearest hatchery by first train, accompanied by a messenger, whose task was to regulate water temperature
by frequent applications of snow or ice to the sacking. Fishing trip8
usually lasted 12-18 h ; if vessels were delayed by contrary winds or
tide, collected eggs were liberated into the sea over the spawning
grounds.
2. Spawn-taking from captive stock at Wo& Hole
The U.S. Fish Commission schooner " Grampus " and two or more
commercial smacks were employed on hand-line fishing for ripening
cod in 10-40 fathoms of water. Each vessel was fitted with a well for
housing captive fish during transport to the hatchery. There they were
transferred by dip-net to large, wooden, floating pounds, moored in
the middle of a wharf-protected basin. Casualties among ripening
stock were usually high-of the 1600 to 9000 fish held annually at
Woods Hole up to the year 1897, not more than 33% yielded eggs.
Dead fish were regularly removed from the pens, and fish ready to
spawn placed in a separate pound for the " stripping " operation.
The spawning of the female cod usually extends over 2 or 3 weeks ;
all oocytes do not mature and enter the oviduct at the same time.
Fish were therefore " stripped " at intervals of a few days until the
ovaries became completely discharged, the " spent " fish being returned
to the sea. About 80% of all eggs taken in a season were fertile.
3. Egg incubation
The Amerioans used two types of incubator for marine fish eggs;
the Chester jar, and the McDonald tidal hatching box. Both devices
incorporated the principle of sea water renewal with intermittent
siphon discharge, thus keeping the eggs in constant motion.
The Chester jar was an ordinary wide-mouthed glass container
about 23 cm diameter and usually 46 cm tall, with a central 12 m m
hole bored in the bottom, fitted with a plug. Roughly 200 000 egga
were introduced into the jar, in sea water, with the plug in position.
The mouth waa then covered with cheese-cloth or linen scrim held fast
by rubber bands, and the jar inverted, under water, to rest on supports
in wooden box fitted with a siphon. Sea water ran in at one end
of the box continuously, and out through the intermittent siphon at