FRESH-WATER MUSSEIvS. l6l 



The equipment for seining and handling the fish consists of a motor boat, one or 

 two flat-bottomed rowboats, seines or other nets, including small dip nets, tanks, 

 buckets, etc. The motor boat is used to cover the various fishing grounds as rapidly 

 as possible to distribute the infected fishes, and to move the outfit from place to place 

 as it becomes advisable or necessary to extend the field of operations. The rowboat is 

 employed in the actual work of seining and handling the fish. If the fish are taken in 

 very large numbers it is convenient to have one or two tanks, similar to the ordinary 

 4-foot galvanized stock tanks and equipped with handles. Under ordinary conditions, 

 tubs serve very well, especially if the fish have to be transported by hand for some dis- 

 tance, as is the case when the fish are taken in rescue work from land-locked ponds or 

 lakes. At times, when the field of operations is at some distance from a place where 

 living and sleeping accommodations can be secured, a camping outfit, or a house boat, is 

 used for quartering the crew. The head of the party must be provided with a dissecting 

 microscope, a magnifying hand lens, and simple dissecting instruments. 



Before an infection can be made, it is first necessary to obtain a supply of glochidia 

 of the desired species of mussels. In localities where commercial shelling is actively prac- 

 ticed this can be done by visiting the shellers' boats and examining the catch for freshly- 

 taken gravid mussels. If it is desired to use the glochidia at once, the brood pouches 

 are immediately cut from the females and placed in water; but if it is desired to use them 

 over a period of several days, the gra\ad shells are purchased and the glochidia removed 

 as needed. In locations where shells are scarce, or where little or no commercial shelling 

 is done, it is sometimes necessary to hire a sheller to procure the mussels. 



The fish are next sought by means of seines or nets, and when secured are sorted and 

 transferred to the tanks or tubs; the fish that are not required for purposes of mussel 

 propagation are immediately liberated in suitable waters. When the containers are 

 comfortably filled with fish, overcrowding being avoided, the brood pouches of one or 

 more mussels, as necessary, are cut out and opened with scissors or scalpel and the 

 glochidia are teased out in a small pail or other container from which they are poured into 

 the tanks with the fish. Figures i to 4, Plate XVIII, show the seining and infection 

 operations in the field. 



The experienced operator can usually tell at a glance whether or not the glochidia 

 are sufficiently ripe for infection. If they freely separate when removed from the brood 

 pouches and placed in a dish of water, it is usually a sign that a sufficient degree of ripe- 

 ness has been obtained. If, however, they adhere in a conglutinate mass and can be 

 separated only with difficulty, it is certain indication that they are unsuitable for 

 infection; examination with a hand lens in such case will show also that the glochidia 

 are still inclosed in the egg membrane, thus reveahng their immaturity. If the glochidia 

 are fully developed, one can readih' determine if they are alive and active by dropping 

 a few particles of salt or a couple of drops of fish blood into a small dish containing some 

 of the glochidia. It is a sign of maturity and vitality if the valves begin to snap together 

 as the salt or blood diffuses through the water. 



After being removed from the brood pouches the life of the glochidia is usually 

 rather short, but it is possible to keep them alive a day or two if the water in which they 

 are retained is changed at frequent intervals and not permitted to become too warm. 



The operator is guided by his experience as to the quantity of glochidia to be placed 

 with a given lot of fish and as to the length of the infection period. The water may be 



