Museum NOotTEs 17

small crustaceans being the favorite feed; as they grow bigger, larger crustaceans, small fish, octopus, etc., are eaten; full grown herrings being eaten by spring salmon.

The measures taken by the Government for the conservation of salmon may be summed up in three categories:

(1) Keeping the rivers free of obstructions or pollution and allowing the fish to go up them to spawn.

(2) Establishment of fish hatcheries. In 1925 the Fisheries Departments dis- tributed 700,000,000 ova—mostly salmon and white fish eggs.

(3) Restriction of fishing by establishing close times, forbidden areas and pre- vention of illegal methods of fishing.

The conservation of the Fraser River salmon is complicated by the fact that the major portion of this run passes along the southern shore of the Strait of San Juan de Fuca in their migration from the sea—there they are trapped in great numbers. Effective regulation of this fishery is only possible by international agreement; to the difficulty in arriving at this is largely due the present smallness of the Fraser River run.

The recent obstruction of the Fraser River at Hell’s Gate Canyon by rock slides has aggravated a situation already serious.

It will at once be realized, from these brief notes, how important a part is played by the “plankton” in the lives of fishes; thus we see that herrings and pilchards live entirely on it, salmon more or less all their lives, and halibut depend on it when young. It can, in fact, be truthfully asserted that nearly all the animal life in the sea is dependent on the “plankton” for its existence, either directly or indirectly; thus its systematic study is necessary to an understanding of the lives of the denizens of the ocean.

If those who have watched the seaweeds and small animals at the bottom of some deep pool on the seashore, and have admired the clearness of the water, had visited the same pool, under similar conditions of the tide, by night, they might have seen the water full of countless specks of light and been able to trace the movements of animals in it by the luminous trails they left behind them—each point of light is produced by some organism; these organisms range upwards in size from bacteria (which measure one ten thousandth of an inch or less in length) and comprise many species. Often large patches of the sea appear cloudy and discoloured, the appearance being due to immense numbers of small creatures, usually of several different species, but sometimes of one species only; they may range from those of microscopic dimension to copepoda an eighth of an inch in length (pl. IL, fig. 1), or small pelagic shrimps about an inch in length (pl. III., fig. 6) ; on these fish may often be watched feeding greedily.

It is these and similar pelagic creatures that form the “plankton.”

In the sea, as on land, the plants form the basis of animal life, converting the gases and mineral salts dissolved in the water into substances that can be utilized as food by animals; in the marine “plankton” this function is largely performed by Duatoms; their distribution and comparative abundance or scarcity are thus of vital importance to the fisheries.

The only information as to their numbers off the B. C. coast is from collections made from the surface every two hours by U.S.S. “Pioneer” on a survey voyage from Seattle to Alaska and back in 1923. To summarize the results,—the number of diatom cells in each pint of surface water averaged about 300,000 near the coast and about