I am investigating whale occurrence off the U.S. mid-Atlantic coast using almost two decades of species presence data. I am interested in learning if the frequency, or overall occurrence, of whales varies over time in the study area off Virginia and North Carolina I've begun exploring the data qualitatively by creating graphs, like the one attached to this message.
I am interested in identifying which statistical tools I can use to quantitatively assess potential patterns of occurrence, including changes over time - in this case across or between years of the study for which we have parallel streams of presence data. These include aerial survey sightings of whales and stranding records (beach cast carcasses) for which we have georeferenced positions and data for the location of six different species of whales.
Effort varies across seasons for aerial surveys and in this graph we quantified effort using the number of sightings of each species per 100 km flown in an attempt to correct for effort. Records of stranded whales are also available and offer a supplemental dataset to investigate occurrence over time. Stranding data were consistently collected annually while aerial survey sightings were focused in cooler water months (winter & spring) although survey efforts did occur in fall and winter. We have aerial survey effort data (km flown) for each year.
Does anyone have suggestions for how I can analyze this data to address the question of whether and what years there may be significant differences in occurrence for each species?
Disclaimer: Data is focused on protected species under the Marine Mammal Protection Act and Endangered Species Act and requires permit specifications to be appended and approved for any presentation or use outside of those requested here.
Thank you for any suggestions you may have to help analyze this data and I am happy to answer any questions.
