01-19-2008, 03:09 AM
[font "arial, helvetica, sans-serif"][#00e010]DNR Develops New Strain of Brown Trout[/#00e010][/font]
[font "arial, helvetica, sans-serif"][black]October 4, 2007
Most anglers know that stocking hatchery-reared trout is a major management tool used by the Michigan Department of Natural Resources Fisheries Division.
In fact, 40% of all recreational fishing in Michigan depends on stocked fish.
Each spring, it is not uncommon to see one of the DNR's 17 fish stocking trucks on its way to plant brown trout and 11 other species of fish in Michigan's waters. In a typical year, these trucks will travel more than 130,000 miles to more than 600 stocking sites across our state.
In 2007, the fish production section of the DNR Fisheries Division planted more than 1.1 million brown trout at more than 370 locations in some 58 counties.
The Fisheries Division produces three different strains of brown trout -- Wild Rose, Gilchrist Creek and Seeforellen.
All three strains are reared at the Harrietta State Fish Hatchery; the Gilchrist strain is raised at the Thompson State Fish Hatchery near Manistique and the Oden State Fish Hatchery near Petoskey rears the Wild Rose and Seeforellen strains of brown trout.
A strain is a group of fish that is genetically distinct from other groups within the same species. Over many generations, a captive population of fish will become genetically less fit for post-stocking survival. This is the case with the Seeforellen strain.
"Over the past several years, we've seen a decline in the survival and return to creel of the Seeforellens," said Ed Eisch, hatchery manager for the northern Lower Peninsula, "so after much discussion, we decided it was time for a change and went looking for a new strain to develop for hatchery rearing."
Eisch said one the first places fisheries biologists looked was the Sturgeon River, located in Cheboygan County, which has long been known to be home to a large population of brown trout.
"Some of those fish stay in the river for the entire year and are known as 'river resident,' Eisch explained. "Others spend a good share of the year in Burt Lake and only migrate up the Sturgeon River as their fall spawning season approaches. These are 'lake-run' fish."
An analysis of both the river-resident fish and the lake-run fish have shown them to be genetically the same, he said.
"Because this population has shown it can thrive in both stream habitat and large lake habitat, these fish looked like the best choice to be the founding stock we needed to establish a new Sturgeon River strain of brown trout."
Last November, after a great deal of discussion and planning, DNR biologists, technicians and fisheries assistants from all over the northern Lower Peninsula converged on the Sturgeon River with stream shocking gear, a fish stocking truck for transportation and hypodermic needles.
That's right -- hypodermic needles.
A preliminary fish health inspection of the brown trout population in the Sturgeon River carried out three months earlier had shown a relatively high prevalence of fish were positive for the bacteria that causes bacterial kidney disease (BKD).
"This did not necessarily mean the fish were sick," said Oden Fish Hatchery Biologist Dan Sampson. "It just meant they were harboring the bacteria and could potentially get sick once they were back at the hatchery. We had to be careful."
After consultation with other DNR fish health staff and the Aquatic Animal Health Lab at Michigan State University, it was determined that a streamside injection of the antibiotic erythromycin would greatly reduce the chances of a BKD breakout in the founding stock once they were back at the hatchery.
"When the fish were collected using the electroshocking gear, they were momentarily immobile which gave me the perfect opportunity to administer the injection before the fish became active," said Sampson.
Over the course of three days, more than 1,250 brown trout ranging from roughly six inches to 20 inches in length were collected and transferred to a raceway at the Oden State Fish Hatchery, where they are being held in isolation away from the rest of the stocks.
"Only three fish were lost during the entire operation," Sampson said. "It went like clockwork."
A sub sample of fish from those captured was sent to MSU for the first in a series of fish health inspections.
According to Sampson, the next step in establishing this strain was getting them to accept the artificial diet of pelletted fish food that hatchery fish are fed. It took several weeks, he said, before the fish were consistently taking the pellets and some never did make the switch to artificial feed.
"They became emaciated and eventually were removed from the population," he said. "To further minimize the chances of a BDK outbreak, another erythromycin injection was administered in July and a third in mid-September."
During the July injections, the fish were inventoried and it was found that some of the fish had become cannibalistic and eaten some of their fellow raceway mates.
A second group of fish was sent to MSU for health inspection in July and the positive affect of the antibiotic was evident.
In mid-September, Eisch said each fish was injected with a PIT (passive integrated transponder) tag which will make it easy to identify individual fish later in their rearing. At the same time, they received their third antibiotic injection in preparation for the upcoming spawning season.
Eisch expects the fish to begin spawning in mid- to late-October and the first of three future brood lots will be collected. These eggs initially will be held in the isolation building.
In January another group of fish will be sent to MSU for a final inspection.
"Assuming the results from that inspection are okay, the young fish can then be moved up to the main hatchery," said Eisch.
If all goes according to plan, the first production-sized lot of Sturgeon River strain brown trout eggs will be collected in 2010 or 2011 for stocking in 2012 or 2013.
[/black][/font]
[font "arial, helvetica, sans-serif"][black]October 4, 2007
Most anglers know that stocking hatchery-reared trout is a major management tool used by the Michigan Department of Natural Resources Fisheries Division.
In fact, 40% of all recreational fishing in Michigan depends on stocked fish.
Each spring, it is not uncommon to see one of the DNR's 17 fish stocking trucks on its way to plant brown trout and 11 other species of fish in Michigan's waters. In a typical year, these trucks will travel more than 130,000 miles to more than 600 stocking sites across our state.
In 2007, the fish production section of the DNR Fisheries Division planted more than 1.1 million brown trout at more than 370 locations in some 58 counties.
The Fisheries Division produces three different strains of brown trout -- Wild Rose, Gilchrist Creek and Seeforellen.
All three strains are reared at the Harrietta State Fish Hatchery; the Gilchrist strain is raised at the Thompson State Fish Hatchery near Manistique and the Oden State Fish Hatchery near Petoskey rears the Wild Rose and Seeforellen strains of brown trout.
A strain is a group of fish that is genetically distinct from other groups within the same species. Over many generations, a captive population of fish will become genetically less fit for post-stocking survival. This is the case with the Seeforellen strain.
"Over the past several years, we've seen a decline in the survival and return to creel of the Seeforellens," said Ed Eisch, hatchery manager for the northern Lower Peninsula, "so after much discussion, we decided it was time for a change and went looking for a new strain to develop for hatchery rearing."
Eisch said one the first places fisheries biologists looked was the Sturgeon River, located in Cheboygan County, which has long been known to be home to a large population of brown trout.
"Some of those fish stay in the river for the entire year and are known as 'river resident,' Eisch explained. "Others spend a good share of the year in Burt Lake and only migrate up the Sturgeon River as their fall spawning season approaches. These are 'lake-run' fish."
An analysis of both the river-resident fish and the lake-run fish have shown them to be genetically the same, he said.
"Because this population has shown it can thrive in both stream habitat and large lake habitat, these fish looked like the best choice to be the founding stock we needed to establish a new Sturgeon River strain of brown trout."
Last November, after a great deal of discussion and planning, DNR biologists, technicians and fisheries assistants from all over the northern Lower Peninsula converged on the Sturgeon River with stream shocking gear, a fish stocking truck for transportation and hypodermic needles.
That's right -- hypodermic needles.
A preliminary fish health inspection of the brown trout population in the Sturgeon River carried out three months earlier had shown a relatively high prevalence of fish were positive for the bacteria that causes bacterial kidney disease (BKD).
"This did not necessarily mean the fish were sick," said Oden Fish Hatchery Biologist Dan Sampson. "It just meant they were harboring the bacteria and could potentially get sick once they were back at the hatchery. We had to be careful."
After consultation with other DNR fish health staff and the Aquatic Animal Health Lab at Michigan State University, it was determined that a streamside injection of the antibiotic erythromycin would greatly reduce the chances of a BKD breakout in the founding stock once they were back at the hatchery.
"When the fish were collected using the electroshocking gear, they were momentarily immobile which gave me the perfect opportunity to administer the injection before the fish became active," said Sampson.
Over the course of three days, more than 1,250 brown trout ranging from roughly six inches to 20 inches in length were collected and transferred to a raceway at the Oden State Fish Hatchery, where they are being held in isolation away from the rest of the stocks.
"Only three fish were lost during the entire operation," Sampson said. "It went like clockwork."
A sub sample of fish from those captured was sent to MSU for the first in a series of fish health inspections.
According to Sampson, the next step in establishing this strain was getting them to accept the artificial diet of pelletted fish food that hatchery fish are fed. It took several weeks, he said, before the fish were consistently taking the pellets and some never did make the switch to artificial feed.
"They became emaciated and eventually were removed from the population," he said. "To further minimize the chances of a BDK outbreak, another erythromycin injection was administered in July and a third in mid-September."
During the July injections, the fish were inventoried and it was found that some of the fish had become cannibalistic and eaten some of their fellow raceway mates.
A second group of fish was sent to MSU for health inspection in July and the positive affect of the antibiotic was evident.
In mid-September, Eisch said each fish was injected with a PIT (passive integrated transponder) tag which will make it easy to identify individual fish later in their rearing. At the same time, they received their third antibiotic injection in preparation for the upcoming spawning season.
Eisch expects the fish to begin spawning in mid- to late-October and the first of three future brood lots will be collected. These eggs initially will be held in the isolation building.
In January another group of fish will be sent to MSU for a final inspection.
"Assuming the results from that inspection are okay, the young fish can then be moved up to the main hatchery," said Eisch.
If all goes according to plan, the first production-sized lot of Sturgeon River strain brown trout eggs will be collected in 2010 or 2011 for stocking in 2012 or 2013.
[/black][/font]