MARINE NATURE NOTES

Otago Daily Times, Issue 22398, 20 October 1934, Page 2

MARINE NATURE NOTES

Written for the Otago Daily Timea. By David H. Graham, F.R.M.S., F.Z.S. ELEPHANT FISH. The -well-known elephant fish can be taken along the whole of the east coast of the South Island, but is more abundant in Blueskin Bay than in deeper water. Nevertheless, it is caught by line fishermen in 100 fathoms. From November to March large hauls are made in from 5 fathoms to 15 fathoms in Blueskin Bay, so much so that it was sometimes impossible to lift the trawl net of the research launch into the cockpit even with block and tackle. One lias to lean over the side and let numbers go before the net can be hauled aboard. In all these hauls it was observed that when red cod were liberated to lighten the net, the Mollyhawks soon devoured them by first pulling out the entrails and then eating the rest; but when elephant fish were liberated, the birds did not even peck at them, let alone eat them. Why this should be so is difficult to imagine, unless the bright, silvery greenish colouring is against the bird’s fancy. Elephant fish were at one time plentiful in Otago Harbour during the summer months, but at present only occasional small runs enter, and they do not stop any length of time. They are most numerous in Blueskin Bay during the summer months, but odd ones are caught during the winter.

There is a diversity of opinion mong fishermen and others as to the maximum size of elephant fish. The largest I have scon measured three feet six inches in length and weighed 12 pounds. Fishermen say they have caught them up to 18 pounds in weight, while a reference from Wellington states that they are caught up to 20 pounds in deep water off Cape Brett. The smallest I have seen measured nine inches in length. My observations go to show that the elephant fish is of a migratory nature and moves to deeper water when cold weather sets in, and then may be hooked in from CO fathoms to SO fathoms by long-line fishermen fishing for groper, but, according to these men, 40 fathoms are the favourite depth in the winter. Fishermen also state that the largest specimens arc caught when they arc hooking. The smaller and medium-sized ones prefer the shallower waters of Blueskin Bay. Elephant fish have a most unusually shaped mouth, which is no doubt the reason why they do not take a baited nook readily. Yet at timea they have been known to bite freely at squid bait, and when they do take to this bait they bite greedily and put up a good fight before being landed. They are really a school fish, but in deep water appear fewer in number, and sometimes only single ones are caught. We have found them in association with skate, red cod, ling, barracoota, groper, kingflsh and all fiat fishes. Whether because of the colouring of elephant fish or of their peculiar shape, they do not appear to have any enemies. Only on one occasion have I found an elephant fish taken as prey; it was 10 inches in length and in the stomach of a red cod caught in Blueskin Bay. The food of elephant fish is moat interesting from a marine biologist’s point of view. It appears to consist principally of mellusca, with Crustacea next in importance. Fish are seldom seen in their stomachs, and then only of such small size that they cannot be said to form much of the diet. The fish found in them were lemon soles 2in to 2sin in length and red cod din to sin in length. When the shape of the mouth of the elephant fish is considered it seems difficult to understand how these other fish were caught. In the shellfish found in their stomachs there was a great variety, no less than 14 distinct species having been identified by me. It seems that bi-valve shellfish (after the pipi style) are the favoured food, but in almost every instance the shells were crushed to pieces by the powerful jaws of the elephant fish. Crabs do not form a great deal of their food and only two species, which did not have a back more than 'Jin in diameter, have been found. On one occasion we caught a good many elephant fish in one haul, and I found some fish with nothing else but these small crabs, and in the same haul fish with nothing elso but shellfish, Whalefeed of the bottom forms is a crustacean frequently seen in their stomachs. One other crustacean on which they feed at times, to the exclusion of all other food, is a shrimp that is found in abundance in Blueskin Bay. Remains of sea eggs were frequently seen and salpa and jelly fish remains were also found in their stomachs, It appears rather strange that this fish should devour and crush such food as hardshelled mollusca and feed on such soft bodied animals as jellyfish. The elephant fish lays her eggs one at a time in the form of capsules similar to the egg case of the skate, but the form is spindle-shaped in outline and bordered by a broad fringe. The tail end is said by some to stick into the mud of the sea floor until the young is hatched, but whether this is so I am unable to say. The upper and lower halves of the capsule are at first united by a membrane, but those found after hatching showed them separated at one end, leaving an opening which the young fish can escape by. The sexes are easily distinguished by the long claspers on the male as well as a moveable clasper, hard in texture which can lie Hat and fit into a specially prepared groove on the top of the head. It is acute and serrated in front, but flat behind. The jaws are armed with large flat plates quite different from those of any other fish. With such a specialised dentition one might well expect the food to be well smashed before reaching the alimentary canal, but it is difficult to understand the diet being so mixed, instead of composed of hardshellcd animals.

The elephant fish belongs to those fish with gristly skeletons and does not possess a backbone as groper and blue cod do. Research has shown that it has a head with a commingling of primitive and advanced anatomical features which give rise to far-reaching questions as to its relationship, not only to other fishes, but to animals such as frogs and lungbreathing forms. It has been maintained that the development of the head, when worked out, will throw much light on the lines of early evolution at a time when the most primitive fishes were beginning to acquire those characters, the possession of which first impelled their changing descendents along the roads of evolution which lead to the higher vertebrates. The elephant fish had an economical value in former times, such as during the war period, when it was sold in considerable quantities and people who did not see it in the original state enjoyed its firm, white flesh and pronounced it a splendid, nutritions fish. Few if anyone in Dunedin will cat it to-day, but large quantities are sold in Christchurch as “ silver trumpeter.” It is a pity that some enterprising firm cannot find time to experiment with this excellent fish and prepare the flesh for export, as it can be caught in large quantities at certain times of the year. Without a by-product plant it is worthless to-day in Dunedin. Line fishermen sometimes resort to elephant fish as bait for catching groper, and consider it fair bait. Although we tried repeatedly to bring live elephant fish to keep in the tanks or ponds, they did not live above eight hours after landing. Apparently they needed a good deal of oxygenated water, more than is possible in a locker or large drum on a research launch. It was

interesting to find so many large worm parasites in this fish. Almost every fish examined by the writer proved to have from one to six of these parasites. The name elephant fish is derived from the fact of its having a protruding snout composed of a gristly nature, which gives it the appearance of an elephant’s trunk in miniature. It is with this protruding appendage that the fish is enabled to dig and secure many of the shellfish found in its stomach. Without tills appendage for digging in the mud, shellfish would be immune from it, as they remain firmly planted end on in the sea bottom, so that it is difficult even for a human hand to dig them.