Using Presence-Absence Data on Areal Units to Model the Ranges and Range Shifts of Select South African Bird Species

Thesis (Ph.D.)--University of Washington, 2013The study of where species occur is an important concern in ecology. Over the last decade, the occupancy model has been the primary tool used in attempts to answer where, when and why species occur where they do. In this dissertation, the occupancy model is improved upon by adding a spatial component to account for similarities between adjacent sites. The model was applied to the Southern ground hornbill (Bucorvus leadbeateri), an elusive species that occurs in low densities through much of sub-Saharan Africa; South Africa is the southernmost end of its range and the distribution of the species there is unknown. The model uncovered new areas of potentially high occupancies, quantified the strong associations between hornbill occurrences and the availability of protected areas, and provided the appropriate structure to ask additional biological questions. The spatial occupancy model was then further adapted to include a temporal component in order to quantify range expansions or contractions when data are collected over time. This model was used on the common myna (Acridotheres tristis), an invasive species in South Africa whose range has been expanding in recent decades. The results suggest that the range of the myna continues to expand at a rate of 3\% a year and that its occurrences are associated with high human population densities

Appendix A. Figure for the number of surveys per site and figures of additional predictive occupancy maps.

Figure for the number of surveys per site and figures of additional predictive occupancy maps

Spatial segregation in eastern North Pacific skate assemblages.

Skates (Rajiformes: Rajoidei) are common mesopredators in marine benthic communities. The spatial associations of individual species and the structure of assemblages are of considerable importance for effective monitoring and management of exploited skate populations. This study investigated the spatial associations of eastern North Pacific (ENP) skates in continental shelf and upper continental slope waters of two regions: central California and the western Gulf of Alaska. Long-term survey data were analyzed using GIS/spatial analysis techniques and regression models to determine distribution (by depth, temperature, and latitude/longitude) and relative abundance of the dominant species in each region. Submersible video data were incorporated for California to facilitate habitat association analysis. We addressed three main questions: 1) Are there regions of differential importance to skates?, 2) Are ENP skate assemblages spatially segregated?, and 3) When skates co-occur, do they differ in size? Skate populations were highly clustered in both regions, on scales of 10s of kilometers; however, high-density regions (i.e., hot spots) were segregated among species. Skate densities and frequencies of occurrence were substantially lower in Alaska as compared to California. Although skates are generally found on soft sediment habitats, Raja rhina exhibited the strongest association with mixed substrates, and R. stellulata catches were greatest on rocky reefs. Size segregation was evident in regions where species overlapped substantially in geographic and depth distribution (e.g., R. rhina and Bathyraja kincaidii off California; B. aleutica and B. interrupta in the Gulf of Alaska). Spatial niche differentiation in skates appears to be more pronounced than previously reported

Spatial analysis results for the central California skate assemblage.

<p>NS = not significant. N = number, WT = weight (kilograms), %FO = frequency of occurrence among hauls, CPUE = catch-per-unit-effort (#/km², kg/km²), ISA = incremental spatial autocorrelation, K = K Function, km = kilometers. Significant p-value thresholds are indicated as follows: * = <0.05, ** = <0.001. Data were collected during National Marine Fisheries Service, Northwest Fisheries Science Center and Alaska Fisheries Science Center trawl surveys (<i>n</i> = 422) conducted during 1997–2010 on the continental shelf and upper slope of central California.</p><p>Spatial analysis results for the central California skate assemblage.</p

Trawl locations among regions in the west-central Gulf of Alaska.

<p>Alaska Department of Fish and Game trawl survey regions located within the larger study site in the western Gulf of Alaska. The total number of trawls conducted during 2003–2012 among regions was, as follows: Kodiak Island (<i>n</i> = 1836), Shelikof Strait (<i>n</i> = 278), Alaska Peninsula (<i>n</i> = 1368), and Kamishak Bay (<i>n</i> = 160).</p

Details of sampling surveys conducted in the western Gulf of Alaska and off central California.

<p>Note: Data were collected yearly for the indicated ranges, with the following exceptions: NMFS–AFSC* = 1998, 2001, 2004; NMFS–AFSC** = 1997, 1999, 2001; NMFS–SWFSC–FED (submersible) = 1992–1994, 1997, 1998, 2002–2004, 2007–2009; western GOA = biennially; Kamishak Bay = 2003–2007, 2010, 2012.</p><p>* = effort was focused on continental shelf,</p><p>** = effort was focused on continental slope;</p><p>NMFS = National Marine Fisheries Service, AFSC = Alaska Fisheries Science Center, NWFSC = Northwest Fisheries Science Center, SWFSC–FED = Southwest Fisheries Science Center–Fisheries Ecology Division, MBARI = Monterey Bay Aquarium Research Institute, ADFG = Alaska Department of Fish and Game, ROV = remotely operated vehicle, N = number of samples for each method, Oct = October, Jan = January, Dec = December, Aug = August, Nov = November, Sept = September, m = meters.</p><p>Details of sampling surveys conducted in the western Gulf of Alaska and off central California.</p

Hot and cold spot maps for species richness of all Californian skates.

<p>Getis-GI Hot spot Analysis Z-score plot of species richness of skates collected from NMFS–AFSC and NMFS–NWFSC trawl surveys conducted during 1997–2010.</p

Original and updated habitat suitability probability profiles for <i>Raja inornata</i>.

<p>Reconstruction of original (A) and updated (B) habitat suitability probability profiles for adult and transitional/adult <i>Raja inornata</i> throughout the U.S. West Coast. The original profile (A) was depicted in the 2005 Essential Fish Habitat Amendment to the Pacific Coast Groundfish Fishery Management Plan (Anonymous 2005). The black line offshore depicts the limit of the U.S. EEZ.</p