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Sand bottom in Oneida Lake is usually found in lagoons and other spots protected from the direct action of the waves. In such places the bulrushes flourish and here are found the best conditions for the growth of the small clams, snails, and insects which form an important element of the food of fish. This photograph of the sand bottom area of the lagoon east of the steamboat landing, Lower South Bay, was taken from a mud bottom habitat in the foreground where the vegetation is more dense but less favorable for mollusks, and illustrates the close relation between the lake fauna and flora and the type of lake bottom. The lagoon is one of the best habitats for the filamentous algæ known as Cladophora
The invertebrate population of a sixteen-inch square of sand bottom under four feet of water. The bivalve mollusk (Sphærium) at the left, the pond snails (Lymnaea) below the center, and small snails (Amnicola) in the lower right-hand corner are in notable predominance. Only five animals other than mollusks were found here, although over the sand bottom as a whole the latter make up only about 50 per cent of the invertebrate life. The mollusks of this lake serve as food especially for the pumpkin seed and the common sucker and indirectly for the bass and pike which eat mollusk-eating fish
STUDIES IN AQUICULTURE OR FRESH-WATER FARMING 481
support with the amount of the biota present. The investigations, in a way, paralleled those carried on in the study of agricultural problems, the environments of the objects studied being quite different.
large number of samples were collected (upward of 800). When sorted and identified this material gave a clear idea of the relation of animals to the different kinds of bottom, to the vegetation, and to each other. A feature of the investigation worthy of mention is the fact that more than twentyfive specialists, many of them in the front rank of America's biologists, coöperated in the identification of the different groups of animals and plants. In this way only can results of a dependable character be obtained.
Fully realizing the significance of the fact that the lake is a microcosm, the problem resolved itself into a study of the relation of the fish fauna to the general physical characteristics of the environment, to the biota as a whole, and to the other members of the fish fauna present in the lake. The data for solving such a problem can be obtained only by making an intensive and exhaustive survey of the body of water. To accomplish this result it was decided to select a limited area of known extent and to study this from several angles. Oneida Lake is 21 miles long and more than five miles wide and has a maximum depth of 55 feet which occurs near the east end of the lake. There are several large bays or indentations which provide admirable localities for habitat studies. One of these, Lower South Bay, situated near the southwest end of the lake, was selected for carrying on the intensive studies planned. This bay is one and five eighths miles long and about a mile wide and contains 881 acres of surface water. It is a comparatively shallow body of water, ranging from a foot or two in depth at the west end to nineteen feet at the east end where it enters the larger lake. It is protected on the west and south sides by the land which rises more or less abruptly from the shore; on the north a long point and several shallows protect it from the rough water. At the east end, however, it is open to the storms from this direction which have a more or less marked influence upon the bay.
In this investigation one of our aims, and perhaps the chief aim, was to ascertain as definitely as possible the actual amount, numerically, of animal life that lived on the bottom or on the vegetation at this time of the year (July). To accomplish this result dredges were constructed to take up a portion of the bottom measuring approximately four inches square or sixteen square inches. On a rocky shore a number of bowlders were carefully removed from the water and all of the life, both animal and vegetal, was removed to vials to be sorted and counted later. Vegetation was carefully taken from the water and the attached animals removed. To minimize the liability of error a
To support a large plant and animal population a body of water must provide varied and suitable conditions, and these are found in Oneida Lake in abundance. Detailed studies indicate that there are three primary types or kinds of these habitats which are more or less distinct. The first includes the headlands or points and some portions of the shore which are shallow and have been swept clean of fine sand and clay, leaving the stones and small bowlders as a rocky pavement, the stones ranging in size from large gravel to huge bowlders several feet in diameter. This type of habitat affords lodgment for many mussels which live in the sand or gravel between the stones, for a multitude of snails which live on the rocks, and for crawfish, insect larvæ, and leeches which live on, under, and between the rocks. The vegetation of such habitats consists of water willow and bulrush.
The second kind of habitat is found in sheltered bays and in other partly protected spots where the force of the waves is somewhat arrested. The bottom is composed of fine sand; the vegetation is abundant, consisting of pickerel weed, bulrush, swamp loosestrife, bur reed, the water lilies, and a few pondweeds (Potamogeton). Many mussels live here, but the most important life is made up of small clams, snails, insects, and other small animals which form such a large proportion of the food of fish.
The third kind of habitat is found in the well protected bays, where there is a mass of vegetation consisting of submerged plants such as pondweeds, hornworts, milfoils, water lilies, and the emergent plants such as pickerel weeds, cat-tails, and bur reeds. The bottom is usually of fine clay or mud. Many fragile snails as well as insect larvæ inhabit this kind of habitat which provides excellent food for fish and other aquatic animals.
The striking feature of the plant life in many habitats, which was constantly forced upon our attention, was the presence of large quantities of the water plants known as filamentous algæ, which covered the bottom as well as the higher plants like a thick blanket, and greatly modified the natural character of the bottom. It seems probable that the great wealth of animal life in parts of this lake is largely due to the presence of this lowly plant, which provides a rich food supply for the invertebrate animals.
In the bays and the shallow areas bordering the shores of this beautiful lake, the floor is carpeted with a great variety of plants, many of which, like the feathery water milfoil (Myriophyllum), form miniature aquatic forests. The rocks, the plants, and the whole bottom in many places are covered with masses of the delicate green water plants, the filamentous algæ.
Among this wealth of plant growth many kinds of animals live in great abundance. The algae are inhabited by the young or larvæ of flies, and small jointed worms related to the earthworms (Oligochæta), whose bodies are as green as the color of the algae which they have eaten. Myriads of little crustaceans, called scuds or water fleas (amphipods and Cladocera), dart about and thousands of fresh-water sow bugs (isopods) crawl over the filmy masses of algae. The little spider-like mites (hydrachnids) actively search the algae and weeds to prey upon the smaller animals. The young or nymphs of dragon flies (Odonata) lie in ambush among the algae or bury themselves in the muddy bottom; the young of May flies, with their feathery gills attached to the outside of the body, and the caddis fly larvæ, with their curious houses or cases made of grains of sand, snail shells, bits of sticks, and plants, crawl over the bottom, dragging after them the houses that protect their soft bodies. Water bugs, water boatmen, beetles, both adult and young, and many kinds of snails complete the variety of this wealth of animal life on the bottom.
The rocky shores afford good foraging ground for many snails, with which are associated the young of May flies (Hexagenia), the flat, disklike larvæ of a beetle (Psephenus), the spiral caddis fly (Helicopsyche), that resembles a snail, and other small animals, such as worms and leeches. The stones on many points are covered with
sponges which look like patches of green velvet through the water. The higher plants afford resting places as well as foraging grounds for many snails, aphids or plant lice, some beetles, and numerous hydras.
The study of this rich storehouse of animal life by the unit area method brought out many facts of interest and importance concerning the distribution of life in this body of water. There are several diverse habitats and the animal and plant life show a corresponding variation. Dividing the bay into three areas, each separated by a contour line at 6, 12, and 18 feet, we find that the greatest development of invertebrate life occurs within the six foot contour. Of the 1164 acres of bottom examined in Lower South Bay and vicinity, 205 acres occur between the shore and the six-foot contour and 959 acres lie beyond this line in deeper water. Careful computations indicate that 88 per cent of the total individual animal life lives in water six feet or less in depth, and that but 12 per cent lives in the deeper water of the area surveyed. When reduced to actual figures, which in a measure are difficult to comprehend, the result shows that upward of 6786 million individuals live in 205 acres in water six feet or less in depth, while but one million individuals live in 959 acres in water deeper than six feet.
When we consider this animal life in relation to acres the results are clearer and can better be compared with acreage productions of land crops. To the acre, the invertebrate animals within the six-foot contour number 33 million individuals, while beyond this line in deeper water the life per acre is but one million individuals, the shallower water being 33 times as productive of life as the deeper acres of the bay. These figures, of course, do not include the plankton, or floating population, only those animals that cling to some support, the bottom or the vegetation. The addition of this population would greatly increase the numerical results, but it was only with the bottom fauna that these studies were concerned.
The population of the 6-12 and 12-18-foot contours does not show such a marked drop in individuals, the water deeper than 12 feet containing 59 per cent of the population of the deeper areas. When we remember that fish life, as well as other aquatic vertebrate life, is more abundant in water six feet or less in depth, and that here the greater number
On the clay and sandy-bottomed portion of Lower South Bay of Oneida Lake the shore is bordered with the typical growth of cat-tails, surrounded on the lake side by American bulrushes. The lake here is only about one foot and a half to four feet deep and well protected from waves, which have a marked effect on vegetation. In all parts of the bay large quantities of vegetable débris are found floating in the water and covering the bottom. Even the dust-fine detritus' is probably a valuable source of food for many of the mollusks and crustaceans, as well as for the bottom mud-eating fish. The bay, with its abundance of vegetation, affords excellent breeding grounds for the fish of the lake, particularly those species which build nests, such as black bass and rock bass
Animals collected on sixteen square inches of clay bottom from the southwest shore of the bay. Caddis fly larvæ, Agraylea and Phryganeida (upper right-hand corner), the snails, Amnicola, the fresh-water sow bugs, Asellus (lower right-hand corner) and scuds (Hyalella) are the more conspicuous forms. These are food for crawfish and frogs which are in turn eaten by pickerel and yellow perch. Bivalve mollusks are notably absent from clay bottoms and altogether in this area there are only half as many mollusks as other animals. When the sand becomes intermixed with the clay, however, the mollusks increase in frequency
The south side of Lower South Bay illustrates the vegetation on sandy clay bottoms, particularly the cat-tails along the shore. These are not found on sand. Bordering the cat-tails on the lake side grow the ever present bulrushes. From the point of view of animal population the most important vegetation in this area is composed of submerged plants and especially the algae which coat the bottom and other plants, and which float in filamentous masses. The alga supply the most valuable vegetable food of the invertebrates of the lake
Invertebrates supplied by one hundred square feet of surface on a log five feet under water. principal forms are the snails (Bythinia and Amnicola) and the scuds (Hyalella knickerbockeri). The latter crustaceans are eaten by fishes and frogs, and are also useful scavengers. It was notable that the sunken log which served as a home for these animals was covered with a thick coating of filamentous algæ and this undoubtedly supplied their chief source of food