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Aquaculture
- Finfish
The distribution of brook trout (Salvelinus fontinalis) includes northeastern North America from the Atlantic seaboard south to Cape Cod, the Appalachian Mountains southward to Georgia, west in the upper Mississippi and Great Lakes drainage to Minnesota and North to Hudson Bay. Their natural range has been greatly expanded through artificial propagation. In Massachusetts, brook trout can be found in 31 of 32 watersheds. Brook trout occur in a wide variety of habitats from small streams to large lakes. Their only true requirements are a year-round supply of cold, well oxygenated water and areas of gravel on which to spawn. As water temperatures rise, stream dwelling brook trout may move downstream to larger bodies of water. Brook trout diet consists of a wide range of aquatic and terrestrial insect and larvae with occasional plant material. Brook trout spawn in late summer or autumn generally in the shallow headwaters of streams or along gravel bars of lakes. Females clear away debris by rapidly fanning the substrate with their tail. Upon completion of spawning, the female covers the eggs with gravel in much the same way she cleared the redd. The number of eggs produced by a female is dependent on body length but may be as high as 5,000. The eggs develop through the winter hatching in about 140 days. Brook trout are raised in large quantities by state facilities for stocking into public lakes and streams. They are also cultured in private facilities for both recreational fishing on site and for stocking into private ponds. Additionally they are utilized by the supermarket and restaurant trade as a food fish. Under culture conditions, brook trout should be maintained at a temperature of about 59° F for optimal growth. The pH should remain close to neutral with an acceptable range of 6.7 to 8.2. As with most salmonid species, dissolved oxygen levels should remain above 5.0 ppm. Brown Trout The distribution of brown trout (Salmo trutta) includes Iceland, the British Isles and the Eurasian mainland from Cape Kanin to the Aral Sea and Afghanistan westward throughout Europe. Brown trout have been widely introduced into many parts of the world. As a result of stocking beginning in the late 1800's, they are widely distributed throughout Massachusetts occurring in 25 of 32 watersheds. The habitat requirements are essentially the same as for brook trout, however brown trout are slightly more tolerant of higher water temperatures. They have been found to survive in waters as high as 80° F. They are frequently found in the slower, deeper pools of streams where they coexists with brook trout. The diet of young brown trout consists of a wide variety of aquatic and terrestrial insects and their larvae as well as fish and other vertebrates. Larger fish feed mainly during the twilight and nighttime hours with fish and crayfish playing a much more important role in their diet. Brown trout spawn in late autumn to early winter as water temperatures approach 45° F. Spawning habitat is essentially the same as for brook trout, namely shallow gravelly headwaters. Generally brook trout have completed spawning before brown trout begin, however. The number of eggs produced by a single female is dependent on body size but ranges from 2,000 to 6,000. The eggs develop over winter in the gravel and hatch in the spring. Brown trout are cultured in large numbers in state facilities for stocking into public waters. Culture also occurs in private facilities mainly for recreational fishing on site and for stocking into private ponds. Under culture conditions, the optimal temperature range for embryo development is 41 to 55° F. For adults, a temperature range of 54 to 66° F should be maintained. The pH should remain between 6.8 and 7.8 while dissolved oxygen levels should be above 5.0 ppm. Rainbow Trout Rainbow trout (Oncorhynchus mykiss) originally occurred in the eastern Pacific Ocean and freshwater west of the Rocky Mountains from northwest Mexico to the Kuskokwim River, Alaska. As a result of introductions outside its range, rainbow trout are now found throughout North America. Additionally, sea-run forms, referred to as steelhead trout, migrate to saltwater then return to freshwater to spawn. They are widely distributed throughout Massachusetts occurring in 23 of 32 watersheds. As with all trout, rainbow trout do best in cold, well oxygenated waters. As with brown trout, however, they are much more tolerant of warmer temperatures than brook trout. They are capable of surviving in waters as high as 85° F provided the water remains well aerated. They occur both in lakes and rivers with moderate flow and gravel substrate. Young fish are generally found in riffle sections of rivers and streams while older fish frequent quiet, deeper pools. Rainbow trout generally feed off the bottom foraging on virtually all aquatic insects and their larvae that occur in their habitats. Where they occur in lakes, fish can become a primary food item. Spawning commences in early spring as water temperatures approach 50° F. Spawning takes place in smaller tributaries of rivers or inlet and outlet streams of lakes and ponds. As with other trout, the female excavates a nest in gravel generally in a riffle above a pool. Eggs are broadcast into the nest then immediately covered with gravel by the female. Eggs numbers may be as high as 12,000 per female. Eggs hatch within two months depending on water temperature with the resulting alevins becoming free swimming within seven days. Rainbow trout are cultured in large numbers at state facilities for stocking into public waters. Culture also occurs in private facilities for recreational fishing on-site, stocking into private ponds and as a food fish for the restaurant and supermarket trade. Culture conditions for rainbow trout are identical to those of brook trout. Temperature should be maintained at about 59° F for optimal growth. The pH should remain close to neutral with an acceptable range of 6.7 to 8.2. As with most salmonid species, dissolved oxygen levels should remain above 5.0 ppm. *Information found at the "White
Paper Project" 
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