Case Study: Blue and Mako Shark Catch Rates in US Atlantic Recreational Fisheries as Potential Indices of Abundance

Generalized linear models were used to derive indices of abundance for blue (Prionace glauca) and shortfin mako (Isurus oxyrinchus) sharks based on two components of the US Atlantic recreational fishery: (1) the private and charter boat recreational anglers covered by the Marine Recreational Fisheries Statistics Survey (MRFSS, 1981-2002) of the National Marine Fisheries Service and (2) Massachusetts shark tournaments (1991-2004). From the MRFSS data, blue shark catch per unit effort (CPUE) showed different trends for different regions, seasons, and fishing modes, implying that CPUE is not tracking blue shark abundance. Mako shark CPUE differed by mode for private versus charter boats, and showed no trend in either boat type. From the Massachusetts tournament data, blue shark CPUE showed different trends north and south of Cape Cod. Mako shark CPUE declined in the late 1990s in Massachusetts tournaments, then increased again in 2002.