The data from sightings suggest a causal correspondence between the distribution of survey effort and the distribution of whales in the Gulf of California

Abstract Data on the distribution of most species are often collected using non-standardized sampling protocols, resulting in biased data due to preferential selection of certain environmental conditions. This study aimed to assess the distribution of survey effort for whale monitoring in the Gulf of California, México and estimate its correlation with environmental variables at different resolutions. This comprehensive database compiles navigation details and species observations from 1982 to 2018. The number of navigation routes for whale monitoring in the Gulf of California was calculated, and 10% and 5% of the best-surveyed cells were located at five different resolutions. Generalized Linear Models were employed to estimate the explanatory capacity of eight environmental variables in the distribution of the survey effort. Only approximately 3%-10% of the entire area can be considered well-surveyed. Collection effort was highest in areas with cold waters, high levels of particulate organic carbon, and phytoplankton, irrespective of resolution. However, regardless of environmental conditions, the distribution of survey efforts correlated with available data on the distribution of whales. These results suggest that the knowledge and prolonged interaction between data collectors and the whale population mainly influence the heterogeneous distribution of survey effort. Understanding biases and associated factors in survey effort distribution may provide insights for future monitoring programs. This knowledge can inform effective conservation strategies for whales in the Gulf of California and beyond.