Feasibility of artificial propagation and introduction of hybrids of the Morone complex into estuarine environments, with a meristic and morphometric description of the hybrids

Laboratory and environmental studies of striped bass (Morone saxatilis) X white perch (M. americana) and striped bass X white bass (M. chrysops) were used to-determine the feasibility of introducing these hybrids into an estuary as a supplement to natural populations of the parental species. Growth patterns, survival, and general hardiness of the hybrids were used as criteria. Growth of striped bass X white perch hybrids in the laboratory was apparently somewhat less than growth of natural populations of striped bass, but was much greater than growth of natural populations of white perch. Hybrid growth was slower than striped bass growth under the same conditions, but hybrid survival was much better than striped bass survival. The hybrids were able to survive and grow in estuarine salinities. Most hybrids matured at two years of age. Striped bass X white bass hybrids were able to adapt to an estuarine environment (the Rappahannock River, Virginia) and could successfully compete with striped bass and other resident ichthyofauna. Hybrid growth was faster than striped bass growth in the Rappahannock and was considerably faster than growth of various freshwater populations of white bass. Hybrids were caught in salinities as high as 17%. They were mature at two years of age. Both hybrids were described using meristic and morphometric characteristics. They were both found to be generally intermediate to the parental species, but in certain traits they tended to resemble one parent more closely than the other. Striped bass, white perch, and their hybrid all had a diploid chromosome number of 48. Possible karyological differences are discussed. One or both hybrids may be suitable for introduction into an estuary to supplement natural populations of striped bass and white perch, but more comprehensive environmental experiments are needed. This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia