Tímarit Verkfræðingafélags Íslands - 01.12.1967, Side 25

TlMARIT VFl 1967
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sustainable yield. 2. Limitations of effort need
to be enforced sooner than later. 3. Complete or
seasonal closing of areas where the mean size is
very small.
The following methods are advised in order
to increase the maximum sustainable yield. 1.
Calculations to find out the optimal mean size
and mean age of the deep sea prawn. 2. Research
on sorting live prawns in machines. 3. Mesh
selection of the deep sea prawn.
The Norway lobster fishery was started in
1958. An attempt is here made to estimate the
maxinum sustainable yield of Norway lobster.
The procedure is the same as that used above
for the deep sea prawn. After trying all the
possibilities from an average effort of 3 years
to that of 8 years, it was found that the best
fit was when the average effort was taken as
a mean of 8 years. The maximum sustainable
yield was calculated for all areas. This came to
about 2905 metric tons per year, while the
average is 3219 metric tons per year for the
years 1960—1966.
The present status of the Norway lobster
fisheries is given by the following:
1. The total effort of 1966 compared to the
optimal average effort (fig. 5 and table 3).
2. The forecasted average effort for 1967
compared to the optimal average efforts years (fig-
5 and table 3).
3. The decrease of average catch per trawling
hour in several areas (table 4).
At present there is no fishery for mollusca.
An account is given of researsh made in Ice-
land on the 2 species Cyprina islandica and
Mytilus edulis. Weighing throughout the year
shows the highest meatweight of Cyprina in the
middle of July (fig.6). After this meatweight
drops rapidly. This is presumably due to spawn-
ing. The chemical analyses show the highest fat
and protein content in the months of May and
June. The best time of year is in those last
mentioned months. More researeh is needed, e.
g. comparison between various localities.
The research on Mytilus carried out in
1957 and 1958 (9, 10) has not been continued.
The meatweight of Mytilus was compared
between several localities and chemical analysis
were carried out. Information was collected on
fishing grounds for Mytilus (previously used
for bait). Further research is needed, e. g. data
on meatweight and chemical analysis throughout
the year.
For both Cyprina and Mytilus more informa-
tion is needed on fishing grounds around the
country.
Mussel poisoning is discussed with reference
to mytilotoxin occuring in Norwegian mussels.
(12). Of the plankton species which are thought
to have caused accumulation of mytilotoxin in
Norway the 2 Peridinium species are also found
hera, while the third Goniaulax tamarensis is
not quite certain. It is not known whether
conditions are ever right to produce enough of
those poisonous plankton species. As the number
of these does not always follow the amount of
poison in mussels it is advisable to measure the
amount of poison in the mussel itself.
Heimildir
(1) Aðalsteinn Sigurðsson og Ingvar Hallgrímsson,
The Deep-Sea Prawn (Pandalus borealis) in Ice-
landic Waters. 1965. Rapp. Cons. Cons. Explor.
Mer 156 105—108.
(2) Ingvar Hallgrímsson og Aðalsteinn Sigurðsson,
Nýting Rækjustofna, Ægir 1967. 9. tbl.
(3) Allen J. A. On the biology of Pandalus borealis
with reference to a population off the Northumber-
land coast. 1959 J. Mar. Biol. Ass. U. K. 189—220.
(4) Unnur Skúladóttir, Aðferð til að meta afurða-
getu rækjustofna í Isafjaðardjúpi og Arnarfirði,
Ægir 1967 5. tbl.
(5) Joyce E. A., Jr and Eldred B. The Florida
shrimping industry. 1966 Fla. Bd. Conserv.,
Educational Ser. No. 15. 47.
(6) Schmidt, E. Rejer og Rejefiskeri ved Grönland,
1966. Skr. fra Danm. Fiskeri- og Havunders., Nr.
26, 91—104.
(7) Gulland, J. A. Fishing and the stockes of fish at
Iceland. 1961. Fish. Invest. Series II, Vol. XXIII,
No. 4.
(8) Unnur Skúladóttir. Leturhumarveiðarnar við Is-
land. 1965. Ægir, 13. tbl.
(9) Dr. Unnsteinn Stefánsson. Skelfiskarannsóknir
sumarið 1957, skýrsla til menntamálaráðs, 1957, 10.
(10) Dr. Unnsteinn Stefánsson. Rannsóknir á kræklingi
í Hvammsfirði sumarið 1958. Skýrsla til mennta-
málaráðs, 1958, 10.
(11) Böhle B. og Wiborg K. F. Forsök með dyrking
av Bláskjell. 1967. Fiskets Gang nr. 24, 391—395.
(12) Oftebro T. og Böhle B. Undersökelser av myti-
lotoxin i bláskjell (Mytilus edulis L.) 1965. Fisken
og Havet, Nr. 1, 6—8.