Farm Fish Ponds in New Zealand

New Zealand Journal of Agriculture, Volume 89, Issue 6, 15 December 1954, Page 546

Farm Fish Ponds in New Zealand

INQUIRIES made by individual farmers to various organisations and departments led • recently to consideration by officers of the Dairy Board, Soil Conservation Council, Department of Agriculture, and Fisheries Branch of the Marine Department of the possibilities of developing farm fish ponds in New Zealand both for recreation and food production. The following article by D. F. Hobbs, Senior Fishery Officer, Marine Department, Wellington, is a synopsis of information and views prepared by the Marine Department.

THOUGH fish farming is centuries J- old and in some countries is very highly developed, there is no readymade system which could easily be adopted for use in New Zealand, and aquiculture would present problems just as varied as those of agriculture. Waters differ just as much in potential productivity as do pieces of land and their management tends to be more complex because of longer food chains (that is, many fish do not feed directly on plant growth as do farm stock, but prey on smaller forms of animal life which eat the plants), and because of predation, differing oxygen and spawning requirements of > various fishes, and difficulties of controlling numbers or even tallying stocks at all. There is, too, a lack of available information regarding fish farming in New Zealand of the type easily obtained for land farming. Much confusion arises because popular accounts of pond farming which reach New Zealand rarely give adequate background facts or draw attention to essential requirements for adopting an established overseas system. In a number of cases tropical or sub-tropical species . of fish are involved which can no more readily be transplanted to New Zealand than could tropical fruits for growing on the high tussock lands. Some of the species involved are vegetarian, some omnivorous, and others live on smaller fishes ■ and aquatic bugs. In eastern

countries and in Europe most fish are produced for food and not for sport. It is very doubtful if even for food the same species, would appeal here. Astonishingly high figures of production per unit area are often quoted without discrimination between crops of fish resulting from natural foraging or from foraging in waters which are artificially fertilised, or again of “stall fed” fish from ponds where both artificial fertilisation and much direct feeding are practised. Whether or not fish farming is necessary or likely to prove popular in any country depends primarily on economic issues. Where the standard of living is very low, labour is cheap, mammalian meat rarely seen, and marine fish resources scanty or remote, pond farming may be almost essential for survival. At the other end of the economic scale food production of fish is subordinated to recreational needs. Thus farm ponds tend to be most popular remote from coastal areas and where rivers and lakes are too scattered or too poor to provide good, handy recreational fishing. Overseas Practices In Europe fish farming has persisted from at least as early as the Middle Ages, chiefly with such species as carp and eels, which have negligible angling value and which in New Zealand would not be esteemed as food. Carp farming in Germany involves in some

cases a rotational system whereby periodically ponds are drained, planted in green crops, and then reflooded and stocked. Sometimes sewage effluent as well is used as a source of basic nutrients. However, the production of carp by use of living matter which develops in sewage effluents has usually as its main object the removal of organic matter and consequential purification of waters which later are recirculated for domestic use. Carp when introduced into North America multiplied in sluggish waters for want of exploitation and this necessitated the introduction of expensive control measures. Recently there has been limited commercial utilisation of carp there by immigrants. Trout production in Europe includes both intensive artificial feeding in small ponds to produce market crops and the stocking of natural waters and major impoundments for recreational use. The records of the little experimental work which has been done on artificial fertilisation of ponds for trout mainly show failure or emphasise serious technical difficulties. For instance, the effort is wasted unless initial acidity of water, where it exists, is first corrected, or if it leads to excessive production of floating plant organisms (phytoplankton) . In China and fairly • generally throughout Asiatic countries fish farming has long been practised. More recently it has been attempted in Palestine and North Africa. Apart from carp (a small ornamental species of which thrives in some warm and sluggish New Zealand waters) this farming involves the use of species

probably all requiring higher water temperatures than would usually be found in New Zealand. The yield per acre often seems at first to be extraordinarily high—sometimes up to 40001 b. per acre in China, but dropping to a maximum of 12001 b. in Palestine and to 4501 b. to 9001 b. in the Philippines. Such farming is conducted in warm, shallow, earth ponds and involves considerable labour. Ponds are usually manured with domestic sewage and garbage and commonly green fodder is added either as direct food or to decompose and fertilise the water. Basically methods are identical with those more recently applied and better documented for goldfish production in the southern states of North America. Indeed such goldfish (a carp species) are one of the fishes intensively cultivated in China. When the very high yields of sometimes a ton or more of fish per acre per annum are examined it is found that they are generally from ponds where direct feeding may be at the rate of 51b. of food for each pound of fish produced and where also fertilisation is at the rate of lib. per pound of fish, a mixture commonly used being one giving 8 per cent, available nitrogen, 8 per cent, available phosphoric acid(P 2 25),O 5 ), and 2 per cent, potash (K 2 O). Generally the efficiency of conversion of basic nutrient matter into fish food will be higher where the aim of fertilisation is the production of plant matter for direct consumption by the fish than where plant matter must be consumed first by very small forms of animal life, which in turn are taken by larger forms, including small fish, on which the largest fish feed. Much of the recent publicity on farm fish ponds has concerned such North American fishes as the black basses and bluegill bream. Usually bass and bream are grown in association and the prolific bream produce a crop of small “pan” fish and also serve as food for the larger, predatory bass. Compared with trout, which prefer temperatures of below 70 degrees F., basses are warm-water species which require a minimum temperature of about 65 degrees to spawn and will tolerate 90 degrees. Despite this, when compared with a number of the tropical species cultivated in Asia and North Africa the basses are fish of the temperate zones. They are strong fighting fish, comparable with the trout, and like it take a variety of lures, including fly. Probably, though, they call for less refined angling techniques than the trout. Bass fight better than the European perch, which is also rather inferior to the trout. An optimum annual yield per acre for bass and bream would be about 1751 b., but the usual yield would be very much less. There are conflicting views as to whether the yield of bass ponds can be improved by artificial fertilisation. When, as often happens, the effect is simply to produce a dense “bloom” of microscopic plants, results may be harmful in that food resources are lowered by the reduction of light penetration into the pond. Unless stocks of bass and bream are rigorously controlled, both as to combined weight relative to the food supply and also as to balance between the two species, cropping efficiency is easily lost. Adequate control necessitates use of ponds which can be de-watered

or in which complete netting is possible, but efficient netting is difficult to achieve if much rooted vegetation grows in a pond and such vegetation may contribute usefully, though indirectly, to food supplies. In North America the farm pond for recreational and food uses has quite recently become popular to supplement inland fisheries in natural waters. By New Zealand standards United States interest in angling seems extraordinary, as a high percentage of the public is attracted to angling despite the small size of trout, congested angling conditions, and inferior fish species. The fishing conditions which reasonably satisfy, very many United States citizens would not satisfy the average New Zealander, who would have no interest in trout of the sizes most usually taken there and who for years has shown scant interest in much better perch fishing in this country than that available and highly popular in parts of the United States. New Zealand Possibilities Recreational fishing in ponds is likely to seem much too tame a sport for the average New Zealander, who derives a good deal of his angling satisfaction not from the capture of fish but from the excuse their pursuit provides him for escaping to backcountry lakes and pleasant river settings. Pond fishing is more likely to appeal to farmers’ children, and seems likely to have limited interest to adults, except as an introduction to angling which would subsequently lead them farther afield. In the two main islands angling facilities of reasonable quality for some of the best game species in the world are fairly widely distributed. The same food motive which has led to fish farming, particularly in eastern countries, is unlikely to be present where meat is readily available at low prices and where marine fish can in many cases be fairly easily obtained. There is thus no reason to expect a boom in pond farming in this country.

It could be developed on a limited scale where special need exists and interest is shown. Any planning would have to take into account present and potential fishery uses of New Zealand’s natural waters and would be bound by certain legal restrictions. Inland Fisheries Policy The Marine Department is generally responsible for the maintenance and development of inland fisheries. Locally administration is in the hands of acclimatisation societies, which any licence holder may join; in a few areas where there is no society the Department of Internal Affairs fulfils the functions of one. Aided by a levy on angling licence fees the Marine Department provides research services. An advisory council, representative of central and local administration and scientific interests, acts as a general co-ordinating and policy-formulating body. In the South Island the distribution and quality of natural waters are such that moderate to good trout fishing is fairly well distributed in relation to population distribution. Moreover, there are no readily accessible and important classes of water potentially valuable for fisheries development. Present utilisation includes all accessible streams and lakes and in the Otago district includes even the stocking of large dredge holes in old goldfields areas and large flooded gravel pits in Canterbury. In the North Island the position is very different. The Taupo and Rotorua lakes provide for many thousands of anglers from the main centres of population at Auckland, Wellington, and elsewhere for whom local streams could not cater sufficiently.' The extraordinary post-war

increase in angling demand has necessitated some change of emphasis in investigational work with greater concentration on improving the yield of the main central North Island lakes and also on bringing new waters into production. Waters being surveyed and studied with a view to future development include a well-distributed series of about 250 small lakes which extend, with some breaks, up the west coast from Otaki to beyond Dargaville. Most of these lie very close to the coast in old consolidated dune country. Additionally streams in the papa country on the east coast and extensive lower reaches of a few major sluggish rivers offer some possibilities for stocking with species other ..than trout. Work on these problems is well in hand, but progress is slow, as it is very necessary to check thoroughly before importing and releasing new species, for mistakes in introduction of new species (of. which mistakes New Zealand has . had plenty . of experience) are never easy to remedy. ’ It seems to be fairly widely accepted that the liberation of bass, both intentionally and accidentally, in trout waters in North America has been harmful to the trout fisheries. Once a fish is introduced it is most difficult to prevent its further spread. Recently the Soil Conservation and Rivers Control Council has shown interest in the possibilities of developing angling in small flood-control and general-purpose farm dams, and at present has in hand the observation and experimental stocking of a few such dams in the Palmerston North area. Legal Restrictions • Basically because the country’s trout and whitebait fisheries are valuable

assets, which should not be jeopardised by misguided releases of new species, there are legal restrictions which should be known by anyone desiring to stock waters. The Fisheries Act applies to all streams, lakes, and ponds except “private waters”. Where the Act applies trout, salmon, and perch may be taken only during the open season by methods and in sizes and quantities permitted in regulations. A licence is necessary except for the occupier of property fishing on his own land. “Private waters”, to which the Act does not apply, are any lying wholly within the land of one owner, but these do not include natural lakes on the boundary of a property or waters over which an owner simply has riparian rights. A farm pond having no outlet stream is clearly outside the scope of the Fisheries Act and the owner is free to . stock and crop it as he wishes, subject only to the limitation that during the closed season for acclimatised fish in that district he may not take any acclimatised fish away from his own property. But where a lake on a farmer’s property has an outlet stream draining through other, property the lake is probably not a private water within the meaning of the Act. The obvious intention of the Act is to ensure that the rights of other persons interested in lower waters should not be jeopardised through the actions of one owner farther upstream. Where it is desired to stock a pond from which drainage enters some stream or river, permission must be obtained from the local acclimatisation society if the species desired is one already present in that stream, or from the Secretary of Marine if it is any other species. Importations of live fish from abroad are strictly controlled both to prevent

introduction of species likely to prove harmful to trout or whitebait fisheries and to lessen the likelihood of establishment of additional parasites or fish diseases. Regulations governing the releases of aquatic organisms can be applied even to private waters. The main purpose is to limit the possibility of, say, fluke-infested snails becoming more widespread. . Construction of Ponds It is impossible to lay down firm rules for the construction of ponds because often use for fishing would be incidental to other uses. In any case shape, size, and details of construction may depend very 'much on the lie of the land, availability of water and ■materials and availability of plant to aid construction. Within limits, however, a pond could .be used for such diverse purposes as control of run-off, as a reservoir for fire fighting, for stock watering, and for swimming and boating beside the production of fish and waterfowl. With judicious planning and planting a pond could well be a beauty spot and a recreational and picnicking centre for the farmer and his family and their friends. A pond is not likely to prove an economic proposition if planned for fish alone, and a general purpose pond need not necessarily cost any more than one constructed for fish. . Subject always to elementary rules of hygiene being observed there is a strong case for cropping fish in domestic water supply reservoirs. The taking of regular fish crops is a way of removing organic matter, and the greater the amount of such matter removed the better generally will be the quality of the water for domestic use. Conversely, the purer a water supply is the less will be its ability to produce a good fish crop.

To provide reasonable angling a pond should be at least i acre or more and should have a maximum depth of not less than 6ft., with some deep water close to the bank so that Snoi Ion? Lnid not marginal weed growth would not mterfere with fishing. An excessive depth—say, 10ft. to 15ft.—would usually be disadvantageous for food production, but a small pocket of deep' water might well afford fish some relief when surface temperatures tended occasionally to rise too high. It is difficult to combine the requirements of fish and waterfowl m the same pond, but a reasonable compromise can be achieved by having a shallow extension at one end for waterfowl and by the provision of nesting cover. The Mallard duck seems better suited to a pond habitat than the grey duck and is much more likplv to nest close bv uxeiy tones iciuse uy. . For adequate control and cropping of stock, and possibly also for control of weeds as a pond matures, it is desirable that the bed of a pond should grade down to an outlet plug which ran bp screened as water is run off This is not, however, imperative where the aim is simply to produce a moderate crop. Provided the bed of a pond is kept clear of snags and is fairly smooth and aquatic plants do not develop excessively nets may assist in cropping and controlling numbers. Even without either draining or netting reasonable control of eels and of any excessive quantities of perch can be achieved with baited eel baskets.

Supply o f Water '. 7 , xi. , x u ~ „ Tt ~n ot necessary that water should J™ nutrient matter® such conditions soluble nutrient matter ould no , t accumulate so usefully as m a pond where the entry of seepage water was balanced by evaporation. However, an artesian bore or a spring supply could assist materially in keepmg the temperatures within moderate nlentv of Ixveen - g inl an Juliet to some na t U ral stream course and it is almost impossible to prevent eels gaining access to any pond that has even an occasional overflow to a watercourse. Generally eels are unwanted because they both compete with useful species or food and prey on them. . Ponds are likely to vary quite as much m productivity as land does and J f dependent on the drainage from surrounding land, may tend to vary according to the quality of the , sue-.. rounding land. Commonly they will be less productive in peaty and other sour formations. Water should preferably be neutral or slightly alkaline and should be clear and not turbid, gSS beds* productive d as would P also any 7 into which a s usne nsion of clav particles was carried ?2SSarlv from hillsidl regularly lrom nillsiae a „x;r; c = I Fertilisation of Ponds r i Artificial rertihsaTion or ronas Artificial fertilisation is wasted ifwater is passing through a pond, - and -. even where it is not it may have

results very different from those desired. Where artificial fertilisation produces a dense flora of microscopic plantS and tUrI J S the water a soupy green the penetration of light is inhibited and useful forms of food do not develop. Reasonably safe treatmen could include the addition of agricultural lime to a new pond if waters were likely to be acid, A pond w hen first filled with water may be as barren of food as a newly ploughed field. If it is filled from a t fS m wlll toffi' wot in „ a iSicuiarlv .yiL stream S r a sluesish P ne In the first summer such wmeed formq l a q t first summer such w and J a ? should also become SbliK The establishmS %f useful “ food organisms could be speeded up and the variety of forms amplified by adding, from an estabiished pond, a few buckets of aquatic weeds including the mullock adhering to their .roots. Bullies and koura (freshwater := crayfish) can .be added, though if the pond is partly surrounded by -narrow, raised sod wall,, koura: might prove troublesome by burrowing in the wall. This is not, however, a usual occurrence with the New Zealand species. Mosquitoes rarely cause trouble in natural ponds They develop mainly j? casual waters largely because- of their ability to populate them more rapidly - than can their natural enemies. The probability is that a few old cans half full of water will produce a far greater quantity of mosquitoes .than . a pond many acres in extent once the pond has an estab-

lished aquatic fauna. Ponds of the depth suitable for fish rearing and containing a normal fauna should never cause any mosquito nuisance. Available Game Fishes There is no probability of bass or other species being imported in the immediate future or of permission being given for their general release if and when they are imported. This means that for angling consideration must meanwhile be limited to species already in New Zealand and which might be obtainable through local acclimatisation societies. Thus the choice lies between brown or rainbow trout and European perch. Trout ' Trout are widely esteemed and (there is no other word for it) “fashionable” in New Zealand. Perch, which are found mainly in lakes and lagoons at places as wide apart as Taieri, Ellesmere, Wairarapa, Foxton, Hawera, southern Hawkes Bay, and even in Hamilton Lake in the Waikato, tend in most places to be rather an unappreciated asset and one which could be made to yield much recreational angling for which reasonable skill would be required. ( The brown trout makes for more skilled fishing than does the rainbow and possibly is tolerant of slightly higher water temperatures. Either trout is superior to the perch as a fighting fish, but both species are inferior to perch as eating fish. Both rainbow trout and perch take a lure more freely than does the brown trout. Though the perch does not take a dry fly like trout, it proves a strong fighting fish if taken with a wet fly on light tackle. Trout prefer cool and well-oxygen-ated water; perch will tolerate waters of considerably higher temperature and containing less oxygen. Trout will not spawn satisfactorily in still water

and thus regular stocking of a pond is necessary; perch spawn on weed in still water and once they are established the problem is usually one of keeping the stock down by heavy exploitation rather than of any further stocking. Trout grow fairly fast but at rates which vary extraordinarily according to the density of stock relative to food supply. Most will mature as 3-year-olds when, depending on food supply, they may weigh as little as Jib. or as much as 51b. or more. A fair annual cropping rate for trout would be 201 b. per acre, with 401 b. to 501 b. as the probable maximum under optimum conditions. Efficient production would call for stocking only with such quantities as could develop rapidly for cropping at good average sizesay, 21b. to 31b.before maturing. There would be no point in permitting any to mature, as spawning would be impossible and food would be uselessly diverted from growth to the production of eggs. No fixed rate of annual stocking can be laid down because production of waters and numbers of predators in them vary very much. Unless and until experience shows otherwise, stocking should never exceed 100 trout of 6in. or 5000 fry of about lin. per acre per annum. Until a new pond has matured and weed and food have had some opportunity to develop in it, it would be unwise to exceed half these 1 numbers. Perch There is little precise information available on cropping of European perch. Under favourable conditions this species will easily reach lib." to 21b. and exceptional individuals 41b. Perch spawn in spring and festoon water weeds with ribbons of eggs. In the absence of weed, as in a newly made pond, it is necessary to add

bundles of twigs. It is probable that with efficient management a far heavier annual crop of perch than of trout could be taken. Whether the perch, however, would be taken at a useful size would depend greatly on the steps taken to stop this prolific species from multiplying excessively and becoming stunted. Commonly in New Zealand a reasonable proportion of perch reach a weight of lib. to 21b. or more, apparently only where predators (chiefly eels) are sufficiently abundant to keep numbers under control. , As eels would to some extent be feeding competitively with perch beside preying on them and are rarely appreciated as food in New Zealand, this form of control is likely to be inefficient. It would be much better to grow a few large trout in the same pond to prey on the young perch or to remove the excess perch when small by netting or by the use of traps of the eel-basket type (which are effective for perch even unbaited), as well as by angling. In most districts the initial stock of perch could be obtained by arrangement with an acclimatisation society. They are very hardy fish and can be transported considerable distances in damp moss in a sack. A dozen or two fish of 4in. to lOin. should within a very few years adequately populate a pond of several acres. Very small fish are excessively bony, but a fish of lOin. and more is. a very good “pan” fish, particularly if it is split open and two fillets are peeled off the skin. A good cropping size is 12in. to Min. and it might be necessary to destroy a considerable proportion of smaller fish to ensure that sufficient quantities reach larger sizes. Side-line Fish , Though there is no likelihood of making a fortune out of goldfish, there is so strong a demand for them

in the larger towns that their production by children in small ponds on farms could be a profitable hobby. .In the absence of eels and other predators they multiply rapidly in shallow, warm ponds rich in food. For this species manuring of ponds sufficiently to turn them a soupy green is . beneficial. Indeed in countries where they are seriously farmed ponds are so enriched that the dense “bloom” of microscopic plants prevents sufficient light penetrating to enable rooted water plants to grow. As goldfish, like perch, spawn on weeds, it then becomes necessary to put in nesting trays of moss lying on wire netting, and the eggs can be conveniently removed to stock other ponds. Under good conditions goldfish reproduce so rapidly that frequent cropping is necessary. This can take the form of culling out the dull-coloured specimens, which are usually in a majority, selling many of the small

coloured ones for aquaria, and producing a few selected large ones, which sometimes reach 21b. to 31b., for ornamental ponds. The same pond which produces goldfish well is almost certain to be invaded by frogs. However, these can be put to profitable use as well, because sometimes the biology departments of the four University Colleges require consignments for dissection and pay quite well for them. They are usually .dispatched alive in per forated cans full of damp weed or moss and are painlessly killed and preserved at their destination.' General Conclusions Conditions in New Zealand differ from those in countries where fish farming is usual, mainly because in New Zealand alternative sources of meat are readily available to all and most of the country is so abundantly provided with rivers and lakes con-

taining good sporting fish. Only the individual farmer whose interest in angling is quite exceptional and who is remote from any good angling water is likely to find it worth while to develop a pond especially for angling. Much more commonly there would be use for general purpose farm dams. These, in addition to meeting more material farm requirements, could be beautified by planting and developed for family recreational needs, which could include swimming, boating, and angling. According to taste the same pond could be to some extent useful for waterfowl either as a sanctuary or for shooting. Suitable species of fish for angling and for food are obtainable through local acclimatisation societies. Anglers and shooters who are members of such bodies are so much dependent on the good will of the farming community both for access and for protection of fish and game that the sympathetic interest of acclimatisation societies • is likely to be readily forthcoming.

THE Waimea Valley in northern Southland consists of numerous * soil .types most of which have one. feature in common —a very tight and impervious subsoil which causes excessively wet soil conditions during .winter. The result' is that spring cultivation is delayed, cereal crops are sown., later, and this delays the harvest, which often becomes difficult because of wet ground conditions. . With winter feed crops a . big percentage of the crop is lost during feeding off. These soils; which are estimated to cover 76,000 acres dry out badly during summer. 'lt is commonly believed that these soils cannot be drained, because they are underlain by a continuous layer of ironstone pan, but this is not true. The Waimea Valley has areas where ironstone formation is more ' prevalent than is usual;, but ironstone formations can be

found in most soils at specific places and particularly in soils with a clayey subsoil. Several areas of 30, 40, and 50 acres throughout the Waimea Valley: have .been drained successfully with spectacular results by mole ' drainage -in association with tile drains, and these areas have-, paved the way for large-scale field., drainage undertakings which it is considered will eventually increase the productive area by at least 80 per cent. The. illustrations above show typical wet conditions in the Waimea Valley (upper) and. a general view of the valley (lower).

—K. L. MAYO,

Instructor in Agriculture, Department of Agriculture, Invercargill