Avoiding Ship-Whale Collisions

Somewhere between acceptable and sustainable: When do impacts to resources become too large in protected areas?

Abstract

Utilization of marine and terrestrial protected areas is fundamentally important for their acceptance and success. Yet even appropriate uses can negatively impact resources requiring managers to make decisions as to when the impacts become unacceptably large. These decisions can be difficult because the level at which impacts occur may be far below the level at which resource persistence is threatened. In Glacier Bay National Park, Alaska, managers must make a recurring decision regarding the number of cruise ships that are allowed to enter the park each year. Cruise ships bring >95% of all visitors to the park but have been involved in several lethal collisions (ship strikes) with humpback whales. Using an individual-based simulation model, we demonstrate that increasing the annual ship volume from current to maximum allowable levels would have negligible impacts on population growth of whales. Over the next 30 years the median number of collisions would likely increase from 3 (95% CI: 0–7) to 4 (1–8) or, worst case scenario, from 5 (0–7) to 8 (3−13), while median annual growth rates would, at most, shift from 4.4% (3.7%–5.2%) to 4.2% (3.5%–4.9%), depending upon assumptions. By comparison, a median of 67 (50–82) ship strikes would need to occur over the next 30 years to threaten the persistence of whales. Confronted with an impact level that is far below what would threaten the conservation of whales, managers are tasked with the decision of placing values on 2 million additional visitors for every additional dead whale. We argue that decision-making related to use-impact trade-offs for protected areas could be more consistent and effective if site-values are defined explicitly, clearly communicated among stakeholders, and linked to biological metrics. Protected areas managers can then utilize monitoring programs to evaluate management effectiveness when the objective is conserving both resources and values.

Gende, S., A. N. Hendrix, and J. Schmidt. 2018. Somewhere between acceptable and sustainable: When do impacts to resources become too large in protected areas? Biological Conservation 223:138-146.

Factors affecting whale detection from large ships in Alaska with implications for whale avoidance

Abstract

In response to growing concern over lethal ship-whale collisions, a number of efforts have been developed intended to enhance the ability of ships to avoid whales. However, the effectiveness of avoidance by large ships depends upon the ships detecting whales at a distance sufficient to allow for an appropriate avoidance measure. Here we explore the issue of whale detection using over 3000 unique detections of humpback whales recorded by observers stationed aboard large cruise ships in Alaska, USA. We used point transect distance sampling methods to generate detection functions necessary to understand the probability of whale detection and how it varies with distance under different environmental and biological characteristics. Detection probability of surfacing whales decreased markedly with increasing distance from the ship. We found visibility and group size to be the most important variables influencing detection. The worst visibility conditions reduced detection probability to near 0 at 1000 m. Compared to detecting a single whale, a group of 2 or 3 whales almost doubled detection probability at 1000 m. Surface active behavior increased detection compared to spouting while showing no flukes. In southeastern Alaska, single whales that spouted during excellent visibility conditions were most commonly encountered and had a detection probability of 0.569 at 1000 m. Understanding the ability of mariners to detect whales at distances sufficient to invoke avoidance measures is a key component in the effectiveness of ‘ships avoiding whales’ and is germane to efforts to reduce lethal ship-whale collisions.

Williams, S. H., S. M. Gende, P. M. Lukacs, and K. Webb. 2016. Factors affecting whale detection from large ships in Alaska with implications for whale avoidance. Endangered Species Research 30:209-223.