Geology topics

Joshua Peirce

Publications and source records attributed to Joshua Peirce.

3 recordsLinked to original sources

USGS2013

Interactions between brown bears and chum salmon at McNeil River, Alaska

Predation on returning runs of adult salmon (Oncorhynchus spp.) can have a large influence on their spawning success. At McNeil River State Game Sanctuary (MRSGS), Alaska, brown bears (Ursus arctos) congregate in high numbers annually along the lower McNeil River to prey upon returning adult chum salmon (O. keta). Low chum salmon escapements into McNeil River since the late 1990s have been proposed as a potential factor contributing to concurrent declines in bear numbers. The objective of this study was to determine the extent of bear predation on chum salmon in McNeil River, especially on pre-spawning fish, and use those data to adjust the escapement goal for the river. In 2005 and 2006, 105 chum salmon were radiotagged at the river mouth and tracked to determine cause and location of death. Below the falls, predators consumed 99% of tagged fish, killing 59% of them before they spawned. Subsequently, the escapement goal was nearly doubled to account for this pre-spawning mortality and to ensure enough salmon to sustain both predators and prey. This approach to integrated fish and wildlife management at MRSGS can serve as a model for other systems where current salmon escapement goals may not account for pre-spawning mortality.

Alaska↗

USGS2011

Radiotelemetry to estimate stream life of adult chum salmon in the McNeil River, Alaska

Estimating salmon escapement is one of the fundamental steps in managing salmon populations. The area-under-the-curve (AUC) method is commonly used to convert periodic aerial survey counts into annual salmon escapement indices. The AUC requires obtaining accurate estimates of stream life (SL) for target species. Traditional methods for estimating SL (e.g., mark–recapture) are not feasible for many populations. Our objective in this study was to determine the average SL of chum salmon Oncorhynchus keta in the McNeil River, Alaska, through radiotelemetry. During the 2005 and 2006 runs, 155 chum salmon were fitted with mortality-indicating radio tags as they entered the McNeil River and tracked until they died. A combination of remote data loggers, aerial surveys, and foot surveys were used to determine the location of fish and provide an estimate of time of death. Higher predation resulted in tagged fish below McNeil Falls having a significantly shorter SL (12.6 d) than those above (21.9 d). The streamwide average SL (13.8 d) for chum salmon at the McNeil River was lower than the regionwide value (17.5 d) previously used to generate AUC indices of chum salmon escapement for the McNeil River. We conclude that radiotelemetry is an effective tool for estimating SL in rivers not well suited to other methods.

Alaska↗

USGS2006

Attacks on sea otters by killer whales

Few references to attacks on sea otters, Enhydra lutris , by killer whales, Orcinus orca , exist in the literature. In an extensive review of predatory and non-predatory interactions between killer whales and other marine mammals, Jefferson et al. (1991) cited only one reference (Nikolaev 1965) in which killer whales aggressively pursued sea otters. In another review of attacks on marine mammals by killer whales in the North Pacific Ocean, Matkin and Saulitis (1994) listed three other interactions between killer whales and sea otters, but with the exception of one personal communication, the references (Barabash-Nikiforov 1938, Tomilin 1957) alluded only to presumed attacks. Kenyon(1969) described only non-aggressive interactions between the two species. No descriptions of killer whale attacks on sea otters have been published. In this note we describe nine observations made between 1992 and 1996 of killer whales attacking sea otters in Prince William Sound and in the Aleutian Islands, Alaska.

Alaska↗