Seismic acquisition causes substantial decrease in catch rates of commercially-important fish

High intensity noise associated with seismic surveys of the sea floor can cause harm or alter the behaviour of aquatic animals. In south eastern Australia, a marine seismic survey (MSS) acquisition area overlapped with commercial fishing grounds on which eastern school whiting (Sillago flindersi) and tiger flathead (Platycephalus richardsoni) are targeted. To assess the effect on commercial catch rates of a MSS, commercial Danish seine vessels were deployed in stratified random surveys of seismic acquisition areas and adjacent control areas within a 11,000 km² fishing ground. Despite the considerable natural spatial and temporal variation in catch rates of each fish species, catch rates were reduced by 99 % for whiting and by 75 % for flathead immediately following the MSS compared with control areas. Significant negative impacts were observed to persist for at least 10 months for whiting. Although randomized survey data were not available from before the MSS, a M-BACI analysis of commercial logbook data in the years preceding and up to 10 months post seismic acquisition revealed a significant reduction in the catch rates of whiting, but not flathead. Cooperative fleet dynamics may have contributed to hyperstability of catch rates masking MSS effects on flathead. The lack of observed mortalities or visible physiological or morphological abnormalities for fish caught post-MSS indicates that either fish moved out of the MSS acquisition area or otherwise avoided capture. Overall, our results demonstrate that impacts of MSS on fisheries can range from negligible to substantial, depending on the species, location and extent of overlap of the MSS acquisition area with fishing grounds.