Comparative Study of Point Intercept Transect (PIT) Method and Underwater Photo Transect (UPT) to Calculate Hard Coral Cover Percentage

Performance of transect and point count underwater visual census methods

A simulation approach was used to study bias and variability of density estimates of fish using the transect and point count underwater visual census methods. Three experiments were conducted to examine the effects of fish density, sampling effort, and the speed of fish in relation to the observer. Fish density and sampling effort did not significantly bias estimates of fish density using eithe...

Seabirds At-Sea Surveys: The Line-Transect Method Outperforms the Point-Transect Alternative

Methods: We tested whether modeling of detection probabilities, and density estimates with their coefficients of variation obtained from the point-transect method provided more robust and precise results than the more commonly used line-transect method. We subdivided our data by species groups (alcids, and aerialist species), and into two behavior categories (flying vs. swimming). We also compu...

Point process models in line transect studies

In visual line transecting, whales are observed when surfacing to breath. Surfacings are short. Point process models for surfacing times are combined with a model for the hazard probability of initial sighting to obtain a likelihood for the observed encounters. Point processes are also useful for describing the clustering of encounters along the track line due to spatial clustering of whales.

Point Transect Surveys for Songbirds: Robust Methodologies

Point transect sampling along linear features.

Distance sampling is a widely used methodology for assessing animal abundance. A key requirement of distance sampling is that samplers (lines or points) are placed according to a randomized design, which ensures that samplers are positioned independently of animals. Often samplers are placed along linear features such as roads, so that bias is expected if animals are not uniformly distributed w...