Night Stocking Sport Fish Species
Q. Why doesn't the Fisheries Division stock fish at night to avoid the avian (bird) predators that can gather in large numbers after a fish planting?
A. There are several reasons why Fisheries Division does not currently stock fish at night. The primary reason is because we feel that only a minimal reduction in predation will occur if we switch to nighttime stocking. There are two key considerations to keep in mind here. First, trout and salmon often remain concentrated at their stocking location for a fairly lengthy period of time, days to weeks, and regardless of the time they are released they will remain in the immediate area for at least several days. Newly stocked fish are vulnerable, easy prey, and consequently they attract predators (both fish eating birds and other fish) as long as they remain in the immediate area. There is no easy way to disperse these newly stocked fish. Predator concentrations will disperse over time as the concentration of their "food" supply drops. Second, in addition to avian (bird) predators that are active in the daytime, there are unobserved "consumers" beneath the waters surface that become more active after nightfall. Piscivorous predators (fish eating fish) such as walleye, brown trout and burbot remain unseen to us at night and consume newly stocked fish. Substantial predatory fish populations are present at almost all of the Great Lakes stocking sites we currently visit each year. The effect of these highly effective night feeders cannot be discounted because they, like any other predator, will concentrate and readily take advantage of an easy meal. There are simply no simple ways to overcome these two key obstacles.
Another thing to keep in mind is that while many seagulls will be seen in the vicinity of fish planting sites, in general seagulls are not very effective fish predators because of their inability to go far below the surface to capture prey. Seagulls do eat some hatchery fish but these typically those that are not as fit as the majority of fish that escape these predators. Terns are only also limited in their ability to consume large numbers of fish as their depth range is fairly shallow although a bit deeper than seagulls.
Q. Are These the Only Reasons Fisheries Division doesn't Stock Fish at Night?
A. No. There are also practical and operational program considerations that need to be addressed when the concept of "night" stocking is considered. While a secondary consideration to the effectiveness of nighttime stocking, Fisheries Division must take into consideration the risks posed at night to our staff as the safety of our handling and stocking personnel is a paramount concern. Loading fish at the hatcheries and stocking by a driver (potentially anywhere in Michigan) are technical activities done with machinery they carry with them an inherent accident risk. As a result, Fisheries Division evaluates any operational changes with great care. Conducting stocking activities at night would compound the existing operational risk for all hatchery personnel involved with stocking and loading. In addition, drivers on the road needing assistance with injuries, fish stress or truck repairs would be at the mercy of whomever they could contact for help after working hours to render assistance. Because safety is emphasized in all of our hatchery operations, we currently have a low accident occurrence rate. Fisheries Division is eager to maintain this low rate and takes a measured approach to any operational change that could have an impact on it. Potentially, these concerns could be minimized but at a very high cost for additional safety equipment and staff as Fisheries Division would have to increase its current staffing to provide a 24 hour safety net for these employees that are working late at night.
In addition to our safety concerns, night stocking would increase the cost to stock fish in Michigan. Night stocking would require additional work hours after the "normal" work shift hours that are needed to maintain hatchery rearing demands at each facility. The extra time needed for night stocking would require additional loading, hatchery staff and driving personnel. This would likely have to be accomplished by paying overtime or shift differential pay or hiring additional staff. Fisheries Division is obligated to rear and stock fish in the most cost-effective manner possible and must realize a substantial program improvement or benefit before an increased cost is mandated statewide. Given the poor likelihood of improved stocking success at this time, we do not see how the increase safety risk and greatly increased costs would offset at best minimal improvements in our fisheries.
Q. Isn't there anything that can be done now to remedy this Frustrating Predation Problem?
A. Yes. Fisheries Division stocking is being coordinated more efficiently than in the past to avoid large migrating groups of avian (bird) predators. Stocking can and is being done earlier in the year before migrating avian predators have arrived en-mass, or conversely after large numbers have migrated through a specific stocking area. We are also coordinating stocking with other control and dispersal efforts on avian (bird) predators to improve survival of our hatchery fish.