Historical standardized CPUEs of seven shark species in the Indian Ocean with preliminary catch estimation
We used an historical longline survey from 1966 to 1989 in the Indian Ocean basin to calculate standardized CPUEs for the blue shark (Prionace glauca), silky shark (Carcharhinus falciformis), tiger shark (Galeocerdo cuvier), silvertip shark (C. albimarginatus), sandbar shark (C. plumbeus), oceanic whitetip (C. longimanus), and shortfin mako (Isurus oxyrinchus), as well as the genera Sphyrna, Alopias, Isurus, and Carcharhinus. Twelve other shark species were recorded in the survey, but were not caught frequently enough to create standardized CPUEs. We use the standardized CPUEs of the blue shark to estimate catches by the Taiwanese longline fleet from 1977 - 1989. These CPUEs represent an important basin-wide baseline for shark abundance at the start of industrialization of Indian Ocean fisheries. We also demonstrate how they can be used in combination with effort data to generate catches for use in stock assessment models. Additionally, we present standardized CPUEs for the porbeagle (Lamna nasus) derived from the IOTC’s publicly available catch and effort data.