Such an increase in penetration depth would have negligible effect on the probability of detection due to the skewed vertical distribution of fish schools. Mature capelin aggregate in schools in shallow water in the spring prior to spawning on gravel beaches along the coast of Newfoundland. This behaviour underlies the basis of an aerial survey program which has been evolving since 1982. The photographic method was limited to sunny conditions with light winds. Digital imagery expanded data collection to overcast conditions and facilitated data analysis.
Video recording appears to improve school detection and is cost-effective.
Aerial surveys of the coastline are designed to collect information on the distribution and surface area of capelin schools as they aggregate in nearshore waters during the spawning season. The distribution of these schools corresponds to availability of capelin in nearby fixed-gear fisheries. The relative abundance index is based on the highest estimate of total area of all schools observed along each transect. Peak estimates are timed to periods of high egg deposition and intense spawning activity. The index assumes that the surface area of capelin schools is proportional to relative abundance.