369 
1919 .] Fletcher.—Lake Taupo and its Trout. 
survive to reach the adult stage : this means that about 1 per cent, of the 
ova would survive to reach the adult stage. The next year, or January, 
1906, our 4,000 trout would have still further increased in weight, and would 
be reckoned at 6 lb., and their ova at 20,000,000. Of these, 200,000 are 
expected to survive to propagate their kind. In 1907 the weight would be 
about 8 lb., and this would mean an increase in the amount of ova too. 
According to the facts already mentioned, the ova would be expected to 
amount to 28,000,000. Reducing this to 1 per cent., it amounts to 280,000. 
At this date we have to take into account the ova from the 60,000 3 lb. 
female trout, the half of the first year’s increase of the 4,000, which would 
amount to 120,000,000, or, reduced to the 1 per cent., 1,200,000. 
In order not to encumber our paper needlessly with long rows of figures 
we pass on to the result of those calculations. We just state that we include 
the 80,000 young trout liberated in January, 1904, and also the same 
number in January, 1905, and include the increase, reckoned in the same 
way, in the results shown. We find the weight of fish at December, 1912, 
would be over 8,000 tons, and the number of young trout at an average 
weight of 3 lb., in addition to the above 8,000 tons, would be 155,000,000. 
If we have been arguing from wrong premises, if our results are too high, 
we have no objection to dividing the totals by ten ; but it would only mean 
that the totals given would be reached by January, 1914, at the latest. 
The trout in the lake are already beginning to feel a shortage of food. 
This is shown by their voracity and the number of thin fish caught early 
in the season. As the small native trout (Galaxias fasciatus) is becoming 
scarce and the brown trout is becoming rare, the lake must either be stocked 
with suitable trout-food or the number of trout considerablv reduced. The 
latter seems to be the more feasible and the more economical. If 
2,000 or 3,000 tons of fish could be taken out of the lake every year no. 
harm would be done, but, rather, the remainder would be the better for such 
a thinning-out. Fish have been smoked by private individuals with great 
success and sent to all parts of the Dominion. An army of men could be 
employed in netting, cleaning, and smoking trout for the breakfast-tables 
of New Zealand. 
The amount of fish taken out of the lake by the ordinary methods of 
fishing can hardly be taken into account in reducing the number. The 
total amount would not be less than 50 tons nor more than 75 tons per 
annum. The shag accounts for far more. A shag would take not less than 
1 lb. of trout per day. Allowing that 5,000 shags make their home on Lake 
Taupo and rivers running into the lake, they would account for 400 tons.* 
This is a very low estimate : I think 1 lb. per shag and 8,000 to 10,000 
shags nearer the mark. 
The decrease in the number of kokopu has led the shag to take toll of 
the young trout much more than they did a few years ago ; but owing to 
the part taken by the shag in transmitting the disease referred to below 
it is possible that steps may be taken to exterminate the shag. 
There have been several references in the public Press to diseased trout. 
The writers seem to have confused leanness with disease. Real disease 
is so rare that not one fisher in twenty knows anything about it. There 
is a parasite that attacks trout, or perhaps is swallowed with its food. 
27—Science. 
