Abundance Estimation of Long‐Diving Animals Using Line Transect Methods

Abstract

Line transect sampling is one of the most widely used methods for estimating the size of wild animal populations. An assumption in standard line transect sampling is that all the animals on the trackline are detected without fail. This assumption tends to be violated for marine mammals with surfacing/diving behaviors. The detection probability on the trackline is estimated using duplicate sightings from double-platform line transect methods. The double-platform methods, however, are insufficient to estimate the abundance of long-diving animals because these animals can be completely missed while the observers pass. We developed a more flexible hazard probability model that incorporates information on surfacing/diving patterns obtained from telemetry data. The model is based on a stochastic point process and is statistically tractable. A simulation study showed that the new model provides near-unbiased abundance estimates, whereas the traditional hazard rate and hazard probability models produce considerably biased estimates. As an illustration, we applied the model to data on the Baird's beaked whale (Berardius bairdii) in the western North Pacific.

Inferring trackline detection probabilities, g(0), for cetaceans from apparent densities in different survey conditions

“…The methods developed recently by Okamura et al . () and Borchers et al . () require diving data to quantify intermittent availability, and these data should ideally be collected at the same time and location as the line‐transect data are collected.…”

“…This subject continues to be an area of active research as shown by several recent publications (Okamura et al . , Borchers et al . , Langrock et al .…”

“…For inconspicuous species like beaked whales and dwarf and pygmy sperm whales ( Kogia simus and K. breviceps , respectively), trackline detection probabilities may be especially dependent on sighting conditions, but values for different sea states have typically not been estimated (Barlow , Okamura et al . , Borchers et al . ).…”

Bio-logging of marine migratory species in the law of the sea

“…This includes, amongst other things, providing data on the interactions of marine species with fisheries [11,12], identification of foraging regions and relationships with static and dynamic ocean features at various scales [13][14][15], and providing data critical for calculating more precise abundance estimates [16,17]. The utility of bio-logging for marine resource management is now widely accepted by marine ecologists and oceanographers [2].…”

“…In "normal circumstances" coastal states shall grant their consent for MSR. 17 Coastal states may withhold consent for research in the EEZ and on the continental shelf that has "direct significance" for natural resources, and those involving drilling on the continental shelf, the use of explosives, or the construction of some artificial islands and structures or that introduce toxic substances into the sea. 18 Furthermore, the coastal State has the right to require the suspension of the research project in progress within its EEZ if it does not comply with these rules.…”