Vol. VI 1 1 



igls"] Mattingley, Cormorants in Relation to Fishes. tg 



in places where there is some cover or protection for their ova 

 which is usually deposited amongst the vegetation in swamps or 

 backwaters where there is a gentle current flowing, or rather 

 filtering through, or in streams amongst the water-weed and 

 other aquatic growths that prevent it being swept away into the 

 swifter parts of the current, and also the ova is placed under logs 

 and stones. On account of the immobility of the ova it is 

 readily preyed upon from below by many kinds of Crustacea 

 such as yabbies, whilst turtles, eels, and other fishes dispose of 

 vast quantities of it, as well as myriads of the small and almost 

 helpless fish fry. Statistics collected by expert pisciculturists 

 and ichthyologists indicate an astounding mortality amono-st the 

 fish ova and fish fry, to an extent almost incredible. The small 

 number of fish that arrive at maturity is out of all proportion to 

 the number of ova deposited. This dire mortality is due to the 

 enemies of the ova and fry, and if the enemies are not held in 

 check then there is a serious diminution in the available supply 

 of mature fish. To destroy those creatures that prey upon the 

 enemies of the fish ova and fry is tantamount to destroyino- the 

 fish themselves, and in the destruction of the Cormorants this 

 procedure is exemplified. To destroy the balance of nature 

 in one direction is merely setting up an evil in another place, 

 and we should be sure of our attitude towards a particular 

 animal or plant ere the consequences of our act recoil 

 unpleasantly on us. The destruction of the Cormorants is an 

 example of this contention — neither ethical nor sentimental 

 regard for birds sways my judgment in this. We must also 

 remember that Cormorants are limited in numbers by the law 

 of nature and do not increase beyond that limit, and we are 

 therefore able to gauge their effect on our fish supply. 

 Cormorants have their natural enemies just the same as other 

 birds and animals, and their increase above the normal number 

 is consequently checked. When approached closely the Shags 

 that build on the reefs and rocky islets in the ocean take fright 

 and fly away, and should there be any Silver Gulls {Larus 

 novcB-hollandicB) and Skuas about the Shags' departure is 

 immediately followed by an invasion of these birds, and it is 

 indeed a sight to see them swoop down upon the Shags' nests 

 and demolish both eggs and young birds. The Gulls smash the 

 eggs by dropping them on the rocks, after which they eat the 

 contents. The Cormorants that nest in inland waters also 

 have their enemies, and it is a fact that a Whistling Eagle's 

 {Haliastur) nest is usually found overlooking their rookeries. 

 Special observations made by me at the Cormorant rookeries, 

 situate on inland waters, show that they feed their young almost 

 entirely on yabbies, frogs, shrimps, and young turtles. One must 

 remember that at this period the swamps, particularly in the 

 Murray River basin, the greatest waterway in Australia, are 



