653 



Abstract— Recreational fisheries in 

 the waters off the northeast U.S. target 

 a variety of pelagic and demersal fish 

 species, and catch and effort data 

 sampled from recreational fisheries are 

 a critical component of the information 

 used in resource evaluation and man- 

 agement. Standardized indices of stock 

 abundance developed from recreational 

 fishei-y catch rates are routinely used in 

 stock assessments. The statistical prop- 

 erties of both simulated and empirical 

 recreational fishery catch-rate data 

 such as those collected by the National 

 Marine Fisheries Service (NMFS) 

 Marine Recreational Fishery Statis- 

 tics Survey (MRFSS) are examined, 

 and the potential effects of different 

 assumptions about the error structure 

 of the catch-rate frequency distribu- 

 tions in computing indices of stock 

 abundance are evaluated. Recreational 

 fishery catch distributions sampled by 

 the MRFSS are highly contagious and 

 overdispersed in relation to the normal 

 distribution and are generally best 

 characterized by the Poisson or nega- 

 tive binomial distributions. The model- 

 ing of both the simulated and empirical 

 MRFSS catch rates indicates that one 

 may draw erroneous conclusions about 

 stock trends by assuming the wrong 

 error distribution in procedures used to 

 developed standardized indices of stock 

 abundance. The results demonstrate 

 the importance of considering not only 

 the overall model fit and significance of 

 classification effects, but also the pos- 

 sible effects of model misspecification, 

 when determining the most appropriate 

 model construction. 



The statistical properties of recreational catch rate 

 data for some fish stocks off the northeast U.S. coast 



Mark Terceiro 



Northeast Fisheries Science Center 

 National Marine Fishenes Service, NOAA 

 166 Water Street 



Woods Hole, Massachusetts 02543 

 E-mail address: mtercer@whsunl wh whoiedu 



Manuscript approved for publication 

 30 January 2003 by Scientific Editor. 



Manuscript received 4 April 2003 at 

 NMFS Scientific Publications Office. 



Fish Bull. 101:653-672 (2003). 



Major recreational fisheries in the wa- 

 ters off the northeast U.S. coast target 

 a wide variety of pelagic and demer- 

 sal fish species (NMFS, 1995, 1996). 

 Fishery data collected in the National 

 Marine Fishery Service ( NMFS ) Marine 

 Recreational Fishery Statistics Survey 

 (MRFSS) are the basis of fishery catch 

 and effort estimates for most of these 

 recreational fisheries and for indices 

 of population abundance used in stock 

 assessments (USDOC, 1992, 2001). For 

 some stocks, reliable fishery-indepen- 

 dent data such as research trawl survey 

 indices are not available, and therefore 

 the recreational fishery data are essen- 

 tial for tracking stock abundance. The 

 intercept (creel sampling) portion of the 

 MRFSS is an interview-type survey of 

 recreational fishing trips and is con- 

 ducted at public fishing sites such as 

 marinas, launching ramps, fishing 

 piers, and beaches. MRFSS catch esti- 

 mates are made by expanding intercept 

 survey sample catch rates in numbers, 

 calculated on a per trip basis, by the 

 estimated total number of recreational 

 fishing trips. The estimated total 

 number of fishing trips is calculated 

 from data collected in a MRFSS tele- 

 phone survey of households located in 

 coastal counties. The U.S. Department 

 of Commerce (USDOC, 1992, 2001) has 

 provided overviews of the MRFSS inter- 

 cept and telephone survey methods and 

 catch estimation procedures. 



In many cases recreational and com- 

 mercial catch rates used as abundance 

 indices are standardized by using 

 general linear models that assume a 

 lognormal error distribution (Gulland, 

 1956; Robson, 1966; Gavaris, 1980; 

 Kimura, 1981). Commercial fishery 

 catch-rate data generally meet tests 

 of normality when log-transformed 



(Gulland, 1956; O'Brien and Mayo, 

 1988). Because of the efficiency and 

 "integrating" property of commercial 

 fishing gear (including trawls, fixed 

 nets, and longlines), even catch rates 

 on a per tow or per set basis are usu- 

 ally lognormally distributed (Taylor, 

 1953). An important characteristic of 

 commercial data is that catch rates of 

 zero (tows or sets with no catch of the 

 target species) are rare. 



With the assumption that there is an 

 underlying lognormal error distribu- 

 tion, general linear models have often 

 been used to standardize recreational 

 fishery catch rates and compute indi- 

 ces of abundance. This approach has 

 been used in the assessments of blue- 

 fin tuna (Brown and Browder, 1994), 

 summer flounder (TerceiroM, black 

 sea bass (NEFSC^), tautog (NEFSC^), 

 winter flounder (NEFSC^), and bluefish 



' Terceiro, M. (ed.). 1993. Assessment 

 of summer flounder (Paralichthys denta- 

 tus), 1993: report of the stock assessment 

 workshop summer flounder working group. 

 Northeast Fisheries Science Center refer- 

 ence document 93-14, 72 p. Northeast 

 Fisheries Science Center, Woods Hole, MA 

 02543. 



- NEFSC (Northeast Fisheries Science Cen- 

 ter). 1996a. Report of the 20th north- 

 east regional stock assessment workshop 

 (20th SAW): Stock Assessment Review 

 Committee (SARC) consensus summary of 

 assessments. Northeast Fisheries Science 

 Center reference document 95-18, 210 p. 

 Northeast Fisheries Science Center, Woods 

 Hole, MA 02542. 



'NEFSC. 1996b. Report of the 21st north- 

 east regional stock assessment workshop 

 (21st SAW): Stock Assessment Review 

 Committee (SARC) consensus summary 

 of assessments. Northeast Fisheries Sci- 

 ence Center reference document 96-05d. 

 200 p. Northeast Fisheries Science Center, 

 Woods Hole, MA 02543. 



