Assessing the population impacts and cost‐effectiveness of a conservation translocation

Abstract

1. Managers often move, or translocate, organisms into habitats that are assumed to be suitable; however, the consequences of these translocations are usually not rigorously assessed. Robust assessment of these management experiments should consider impacts to both donor and recipient populations and compare the costeffectiveness of translocations to other actions.2. Here we evaluate the translocations of a federally listed fish species, humpback chub within a tributary to the Colorado River in its Grand Canyon reach (Arizona, USA). We analyse mark-recapture data with multistate models to estimate vital rates (growth, survival and movement) for the donor and recipient populations while accounting for substantial temporal variation in vital rates. We then use stochastic matrix projections to quantify the impact of translocations on adult population size. Lastly, we compare the costs of translocations to another, legally required management action, non-native fish removal, by modifying an existing bioeconomic model.3. We estimate that six of eight translocations during the study period positively impacted adult abundance and that the overall population impact was positive.Population projections suggest that each chub translocated per year increases the equilibrium adult population size by 1.2 (95% CI: 0.4-2.2) adults, lessening the need for non-native fish removal.4. The continuation of translocations at the current rate is expected to save managers ~$50,000 per year by decreasing the annual probability of removals from 0.26 to 0.15. Further savings and decreases in removals could be attained by avoiding translocations in years when there has been no winter/spring runoff and modifying the number of translocated individuals based on the estimates of juvenile production in the lower Little Colorado River. Synthesis and applications.Translocations that increase the abundance of a rare species can sometimes be viewed as a hedge against future declines that might necessitate more costly interventions. Quantifying population benefits and economic costs of management actions like translocations and comparing alternative actions can lead to cost-effective conservation that is more easily sustained.

Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations

“…We leveraged detection data from multiple monitoring programs throughout the CRE allowing for improved survival estimates accounting for emigration. These survival estimates (annual mean survival = 0.60 and 0.35, Havasu and Shinumo, respectively) were comparable with those found for juvenile humpback chub in the source population (Dzul et al, 2016;Yackulic et al, 2014), and slightly lower, for Shinumo, to fish translocated to the upper LCR (Yackulic et al, 2021). We also estimated lower survival for in situ-produced fish, which could have been a function of unaccounted for tag-loss in the field.…”

Quantifying flow and nonflow management impacts on an endangered fish by integrating data, research, and expert opinion

“…While reducing uncertainty in RGSM abundance, vital rates, and management effectiveness would improve scientific understanding, further reductions in uncertainty may not be necessary to identify the best set of management actions. Future analyses could build on the work described here by estimating the impacts to other resources of the various flow and nonflow actions and engaging in multi-objective trade-off analysis (e.g., Runge et al, 2015Runge et al, , 2018 and/or by identifying the most cost-effective solution to meeting management goals (Donovan et al, 2019;Yackulic et al, 2021). A common feature of these analyses is quantification of the value of perfect information (i.e., the extent to which decreasing scientific uncertainty is expected to lead to better management decisions; Canessa et al, 2015).…”

“…Disentangling impacts on different life stages from multiple actions is frequently not feasible using simple analyses of a single data type and necessitates more sophisticated models that integrate multiple sources of information and represent the age, size, or stage structure of the focal species. For many animal species, mark-recapture studies provide the most robust estimates of many demographic rates and can be used to determine how environmental conditions or management actions affect the demography of a particular age, size class, or stage in a population (Williams et al, 2002) and scale up to affect overall adult abundance (e.g., Yackulic et al, 2018Yackulic et al, , 2021. Other approaches (e.g., occupancy or count data) can also often provide useful estimates of abundance and even demographic rates (e.g., Zipkin et al, 2017).…”

Predicting harvest impact and establishment success when translocating highly mobile and endangered species

“…Dimond & Armstrong, 2007; Furlan et al, 2020), but translocating too few individuals will reduce the probability of establishing a population at the destination site (e.g. Yackulic et al, 2021). This trade‐off can sometimes be solved by establishing captive populations that become sources for translocations, but captivity is not an option for every species (Canessa, Converse, et al, 2016).…”