THE ARTIFICIAL PROPAGATION OF MARINE FISH
13
on down the line. If boxes were stocked with eggs at this juncture,
incoming flow tended to drive them into those corners farthest from
the supply. To counteract this, Dannevig contrived an up and down
movement of the free end of each box, by mechanically raising and
lowering an iron rod mounted above the longitudinal partition of the
trough. The upper end of this rod was hinged, while the lower end was
linked to an eccentric wheel driven by the outflowing sea water from
the trough. Transverse lugs, fastened to the rod, rested on the free
edges of each box, so that a slow upward movement of the rod, followed
by a sudden fall, produced a similar movement of incubators. This
intermittent rocking motion prevented the accumulation of eggs at the
surface or in corners, thus incressing the production potential of the
incubators, each of which could hold 676000 cod eggs (Dannevig,
1910a) with reasonable survival to hatching, compared with 380 000
eggs per larger incubator at Woods Hole (Brice, 1898).
Dannevig (1928) reported that newly-hatched cod larvae were
subsequently sold at a price one-third of cost to fiord fishery associations, and transported to their point of liberation in watertight boxes
fitted with En inner fabric container. He found it possible to keep
brood alive for 24 h in these conditions, and, with a boat capable of
7 knots, was thus able to supply the whole of the Skagerrak coast of
Norway, from the Swedish border to west of Lindesnes.
The British sea-fish hatcheries used the Dannevig technology, with
minor differences in detail. At Piel, for instance, insufEcient funds
were available for the construction of a spawning pond, and ripening
fish (plaice and flounders) had to be housed in totally inadequate
laboratory tanks (Scott, 1903). The spawning ponds at Port Erin
were not usually irrigated with a continuous supply of sea water,
merely " topped-up '' from time to time. Eggs were not automatically
collected by outflowing surface currents, but fished manually with E
fine-mesh floating net. Filtration techniques varied from hatchery
to hatchery ; whereas the Norwegians relied on sand filters (Dannevig,
1928) coarse towelling was used at the Irish Sea establishments (Scott,
1%; Herdman, 1908).
IV. THE PRACTICAL VALUE OF MARINE FISH HATCHING
The pioneers of sea-fish hatching were motivated by the simple
hypothesis that the annual brood strength of a fish species is directly
Proportional to the number of eggs liberated by the adult stock. They
were therefore very concerped at the loss of spawn resulting from the
fishing of spal&ng aggregations. Having found that the eggs
Of 8 sea fish could be artificially fertilized, it seemed a logical step
13
on down the line. If boxes were stocked with eggs at this juncture,
incoming flow tended to drive them into those corners farthest from
the supply. To counteract this, Dannevig contrived an up and down
movement of the free end of each box, by mechanically raising and
lowering an iron rod mounted above the longitudinal partition of the
trough. The upper end of this rod was hinged, while the lower end was
linked to an eccentric wheel driven by the outflowing sea water from
the trough. Transverse lugs, fastened to the rod, rested on the free
edges of each box, so that a slow upward movement of the rod, followed
by a sudden fall, produced a similar movement of incubators. This
intermittent rocking motion prevented the accumulation of eggs at the
surface or in corners, thus incressing the production potential of the
incubators, each of which could hold 676000 cod eggs (Dannevig,
1910a) with reasonable survival to hatching, compared with 380 000
eggs per larger incubator at Woods Hole (Brice, 1898).
Dannevig (1928) reported that newly-hatched cod larvae were
subsequently sold at a price one-third of cost to fiord fishery associations, and transported to their point of liberation in watertight boxes
fitted with En inner fabric container. He found it possible to keep
brood alive for 24 h in these conditions, and, with a boat capable of
7 knots, was thus able to supply the whole of the Skagerrak coast of
Norway, from the Swedish border to west of Lindesnes.
The British sea-fish hatcheries used the Dannevig technology, with
minor differences in detail. At Piel, for instance, insufEcient funds
were available for the construction of a spawning pond, and ripening
fish (plaice and flounders) had to be housed in totally inadequate
laboratory tanks (Scott, 1903). The spawning ponds at Port Erin
were not usually irrigated with a continuous supply of sea water,
merely " topped-up '' from time to time. Eggs were not automatically
collected by outflowing surface currents, but fished manually with E
fine-mesh floating net. Filtration techniques varied from hatchery
to hatchery ; whereas the Norwegians relied on sand filters (Dannevig,
1928) coarse towelling was used at the Irish Sea establishments (Scott,
1%; Herdman, 1908).
IV. THE PRACTICAL VALUE OF MARINE FISH HATCHING
The pioneers of sea-fish hatching were motivated by the simple
hypothesis that the annual brood strength of a fish species is directly
Proportional to the number of eggs liberated by the adult stock. They
were therefore very concerped at the loss of spawn resulting from the
fishing of spal&ng aggregations. Having found that the eggs
Of 8 sea fish could be artificially fertilized, it seemed a logical step