=Herring, Alewives, and Sardine.=--The herring is a much smaller fish than the cod, and, commercially, is much less important. They school in about the same waters as the cod, but are caught at a different season, gill-nets being usually employed. Practically no distinction is made between full-grown herring and alewives of the same size. The fish are usually cured by smoking, pickling, or salting, and in this form are either exported or sold in interior markets. The true sardine is found in latitudes a little farther south than the schooling-grounds of the cod. The most important fisheries are along the coasts of the Latin states of Europe. Sardine fishing is a great industry all along the New England coast of the United States, but the "sardines" marketed from this region are young herring. Indeed, nearly all sorts of small fry are sold in boxes bearing spurious French labels. =Salmon.=--Most of the salmon are caught in the rivers flowing into the North Pacific Ocean. The fish are caught in traps and weirs at the time of the spring run, when they ascend the river to spawn. The rivers are frequently so congested with the salmon that thousands of tons are caught in a single stream during the run. The salmon canneries of the Columbia River are very extensive establishments, but in the past few years they have been surpassed by the Alaskan fisheries, which produce not far from fifty million pounds each year. The dressed fish is cooked by steam, canned, and exported to all parts of the world. The growth and development of the industry has also made an enormous demand on the tin mines of the world. Canned salmon is the largest fish export of the United States. There are extensive salmon-fisheries in Norway, Japan, and Russia. =Other Fish.=--_Mackerel_ and _haddock_ are caught near the shores of the North Atlantic. Most of the mackerel-catch is pickled in brine and sold in small kegs known as "kits." The _menhaden_-catch of the North Atlantic is converted into fertilizer. The _halibut_ is a large fish that is rarely preserved. The area in which it is caught is about the same as that of the cod. _Shad_ are usually caught when ascending the rivers of the middle Atlantic coast. In the United States, Chesapeake, Delaware, and New York Bays yield the chief supply. The _bluefish_ and _barracuda_ are warm-water fish. The market for fresh fish has been greatly enlarged by the use of refrigerator-cars. The _sturgeon_ is captured mainly in the rivers and lakes of the temperate zone. Those of the Black Sea sometimes attain a weight of 2,000 pounds. The flesh is of less importance than the eggs, of which caviare is made. Russian caviare is sold all over Europe and America, and not a small part of the product is made in Maine. The caviare made from the roe of the Delaware River sturgeon is exported to Germany. The _tunny_ is confined to Mediterranean waters.