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Alexander James Gatch

Publications and source records attributed to Alexander James Gatch.

3 recordsLinked to original sources

Key considerations for decision makers and stakeholders when identifying source populations for conservation translocations of fishes

Conservation translocations are undertaken to increase the viability of imperiled organisms and/or restore ecosystem functions or processes. A key step in the conservation translocation process is to decide which source or founder population is most likely to lead to translocation success. Existing guidance to inform this decision includes a variety of considerations, but few documents focus solely on this step. Furthermore, despite the importance of stakeholder engagement to long-term conservation success, guidance for selecting source populations rarely describes approaches for stakeholder inclusion. Herein, we undertook a literature review for fish conservation translocations and summarized key considerations (e.g., genetics, habitat, life history, effects on source or recipient populations and ecosystems, logistical) to be used when selecting candidate source populations. We describe the importance of including stakeholders and recommend that decision makers coproduce the source population decision with them. We propose a structured expert judgment approach to assess the probability that specific aspects of these considerations could be achieved for each candidate source population. Finally, we recommend synthesizing results of the expert judgement process to enable decision makers and, ideally, invited stakeholders to choose which source population(s) based on their previously identified fundamental objectives. Although we developed this approach for fishes, it could be used for other conservation translocation efforts where stakeholder involvement and synthesis of support for different source populations are deemed valuable in the planning process.

Global Ecology and Conservation↗

Factors affecting short-term post-release survival probability of Lake Trout implanted with acoustic telemetry transmitters

The use of acoustic telemetry is steadily expanding to help answer questions related to habitat use, movement, and behavior of fishes. Significant time and resources are invested to start acoustic telemetry studies; therefore, careful planning is needed to limit post-release mortality of tagged individuals. Deep, cold-water species present additional challenges to acoustic tagging because of changes in temperature and pressure experienced during capture. The objective of our study was to determine if capture method, surface water temperature, water depth, or fish size influenced short-term post-release survival of a deep, cold-water species, Lake Trout Salvelinus namaycush . In 2023, 299 Lake Trout were captured with angling or gillnets across Lake Ontario (Laurentian Great Lake – U.S. & CAN) and surgically implanted with acoustic transmitters. We estimated 30-day post-release mortality and 24-h post-release distance traveled for tagged Lake Trout. We used Cox proportional hazards models to identify factors affecting survival probability and multiple linear regression to identify factors affecting post-release distance traveled. Thirty-day post-release mortality was minimal (9.03 %, 27/299 Lake Trout); however, mortality was 6.37 times more likely for Lake Trout captured in gillnets compare to angling ( p = 0.003). Lake Trout length had a marginally significant effect on mortality ( p = 0.052) but capture depth and temperature did not ( p > 0.05). Lake Trout post-release distance traveled was not significantly influenced by capture gear, depth, temperature, or Lake Trout length ( p = 0.61). Our results indicate that tagging-induced post-release mortality is minimal for Lake Trout tagged in the spring, but survival can be increased by avoiding use of gillnets.

Lake Ontario↗

Egg size scales negatively with system size in a periodic fish species

Optimal egg size theory implies that female organisms balance between fecundity and individual offspring investment according to their environment. Past interspecific studies suggest that fishes in large marine systems generally produce smaller eggs than those in small freshwater systems. We tested whether intraspecific egg size variation reflected a similar pattern by comparing egg size among yellow perch ( Perca flavescens ) populations inhabiting a range of system sizes. In 2018, 2019, and 2023, we collected yellow perch egg samples from 12 locations in systems ranging in surface area from 37 to 5,390,492 ha. First, we found that egg diameter significantly increased with maternal total length in five of eight individually tested populations. After accounting for these maternal effects, we found a significant interaction, where females inhabiting larger lakes, such as the main basins of Lakes Erie and Michigan, produced smaller eggs than those in smaller inland lakes, and the greatest differences were demonstrated among females of greater total length. This egg size variation in the largest females is consistent with interspecific egg size comparisons between marine and freshwater fishes. However, by examining a single species across vastly different environments, we were able to support theoretical expectations that maternal investment in offspring should vary with environmental conditions controlling early-life resource acquisition and competition.

Ecology and Evolution↗