M
Mike
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- Nov 10, 2006
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As I posted in another thread, PFBC rainbows are fall spawners. I have also confirmed that PFBC golden rainbows are fall spawners as well. What I should have said, however, is that the vast majority are fall spawners; a very low percentage of the females mature through the winter. Likewise, some males mature through the winter or remain ripe throughout late fall and winter; thus, the spawning freshly stocked golden rainbows (1 male, 1 female) in Ontelaunee Creek in early March and the attendance by three much smaller 1.5-2 yr. old male rainbows. Not all of the fish mature at the same time (fall), but the vast majority do so. In nature there can be adaptive advantages to protracted spawning periods for a given species, but the majority usually spawn when on average historical conditions have been best. Also, it is possible that the natural spring spawning behavior has not been completely selected out of the hatchery population.
With a few exceptions, most successful rainbow trout populations in Pa are in limestone streams, where water temps are relatively constant. Note that I said populations, which does not mean the occasional fish. Some are fall spawning populations; most are spring spawning populations. I am aware of one or two freestone populations in NW Pa. Despite the wide stocking of rainbows across the state, few populations have developed. Why? 1. Water temperatures less than 42 degrees F negatively affect the survival of deposited rainbow eggs. So, in the vast majority of Pa streams, winter water temps would kill otherwise viable eggs. 2. Water temps higher than 56 deg F negatively affect the development of eggs in the female RT. Most Pa streams exceed 56 deg F in summer. It would not surprise me if these temperature minimums and maximums vary slightly from strain to strain, but the principle remains the same. In a real life example, both 1. and 2. would explain why, despite holdover of some RT in Tulpehocken Creek's DH area, little or no successful reproduction occurs. The very limited reproduction that is successful is probably so because there are rainbows residing in Plum and Cacoosing Creeks, which are limestone tribs.
And just to clarify something, two year old rainbows carry eggs and could be spawned in Pa.'s hatcheries, but three year olds have more and larger eggs. Brood stock is primarily comprised of three year olds in Pa hatcheries. As trout age percent egg viability declines so there is no real advantage to keeping even larger and older fish in the hatcheries as brood. One can use more younger fish (3 yr olds) to get an equal number of eggs that are more viable than those produced by older fish. And older, larger fish are more expensive to raise.
With a few exceptions, most successful rainbow trout populations in Pa are in limestone streams, where water temps are relatively constant. Note that I said populations, which does not mean the occasional fish. Some are fall spawning populations; most are spring spawning populations. I am aware of one or two freestone populations in NW Pa. Despite the wide stocking of rainbows across the state, few populations have developed. Why? 1. Water temperatures less than 42 degrees F negatively affect the survival of deposited rainbow eggs. So, in the vast majority of Pa streams, winter water temps would kill otherwise viable eggs. 2. Water temps higher than 56 deg F negatively affect the development of eggs in the female RT. Most Pa streams exceed 56 deg F in summer. It would not surprise me if these temperature minimums and maximums vary slightly from strain to strain, but the principle remains the same. In a real life example, both 1. and 2. would explain why, despite holdover of some RT in Tulpehocken Creek's DH area, little or no successful reproduction occurs. The very limited reproduction that is successful is probably so because there are rainbows residing in Plum and Cacoosing Creeks, which are limestone tribs.
And just to clarify something, two year old rainbows carry eggs and could be spawned in Pa.'s hatcheries, but three year olds have more and larger eggs. Brood stock is primarily comprised of three year olds in Pa hatcheries. As trout age percent egg viability declines so there is no real advantage to keeping even larger and older fish in the hatcheries as brood. One can use more younger fish (3 yr olds) to get an equal number of eggs that are more viable than those produced by older fish. And older, larger fish are more expensive to raise.
