82 



Fishery Bulletin 100(1) 



fish caught from North Carolina to Florida with fishery- 

 independent gear during 1979-81 and 1988-94. Nelson 

 ( 1988) aged red porgy with scales (?! = 126) from fish caught 

 in the northwestern Gulf of Mexico with fishery-indepen- 

 dent hook-and-line gear and trap gear during 1980-82. In 

 the eastern Gulf of Mexico, Hood and Johnson (2000) aged 

 red porgy from sectioned otoliths (^=852) collected from 

 headboat and commercial catches during 1995-96. Vassi- 

 lopoulou and Papaconstantinou (1992) used scales from 

 138 red porgy that were taken with fishery-independent 

 hook and line and trammel nets in the Mediterranean Sea 

 during 1985-86, and Serafim and Krug (1995) aged red 

 porgy from whole otoliths (?!=358) that were collected by 

 using commercial longlines and fishery-independent gear 

 in the Azores during 1991-93. Researchers in the Canary 

 Islands aged 1505 red porgy from commercial trap and 

 longline samples during 1985-86 and 1991-93 (Pajuelo 

 and Lorenzo, 1996), and researchers off the Argentinian 

 coast used trawl-caught samples during 1972-81 to obtain 

 5859 red porgy that were aged from scales (Cotrina and 

 Raimondo, 1997). 



Predictions offish populations from models rely heavily 

 on input data sets, including age and growth. If samples 

 used in the aging study are not representative of the en- 

 tire population (i.e. the entire geogi'aphic range of the 

 stock, full range of fish size, and different gear types), 

 model predictions (e.g. spawning potential ratio |SPR|) 

 can mislead management decisions. A comparative stock 

 assessment of red porgy was done by using growth pa- 

 rameters and age-length keys generated from two stud- 

 ies: 1) fishery-independent data (Harris and McGovern, 

 1997) and 2) fishery-dependent data (Manooch and Hunts- 

 man, 1977; Potts et al.'M. Each set of age and growth data 

 was applied to fishery-dependent landings and length fre- 

 quencies. The fishery-independent age and growth data 

 produced a static SPR of 46^^^, which is well above the 

 overfished definition (SPR<30'7f) as set forth by the South 

 Atlantic Fishery Management Council (SAFMC). The fish- 

 ery-dependent age and growth data produced a static SPR 

 of 19*7^ (Potts et al.''), which makes red porgy, by definition, 

 overfished and which necessitates that stringent manage- 

 ment measures be put in place to protect the stock. 



The purpose of our study was to update the age and 

 growth information on red porgy caught in the recreation- 

 al and commercial fisheries operating along the southeast- 

 ern United States. We present the von Bertalanffy growth 

 model, weight-length relationship, and age-length keys 

 for red porgy collected from the headboat hook-and-line 

 fishery, commercial hook-and-line fishery, and fishery-in- 

 dependent samples. We also compare mean age at length 

 of red porgy collected from recreational fisheries, commer- 

 cial fisheries, and fishery-independent sources. We discuss 

 how data source selection affects the growth parameters. 



Materials and methods 



Sagittal otoliths were collected from red porgy landed by 

 hook-and-line fishermen from the headboat (recreational) 

 fishery («=249) between 1989 and 1998 (59% from 1996 to 

 1998) and the commercial fishery (n=264) between 1997 

 and 1998 operating from North Carolina to southeast Flor- 

 ida. From the two fisheries, 64% of the samples came 

 from North Carolina, 14% from South Carolina, and 22% 

 from the east coast of Florida. Because of minimum size 

 limit regulations (305 mm total length), the South Caro- 

 lina Department of Natural Resources (SCDNR) Marine 

 Monitoring and Prediction (MARMAP) Program supplied 

 us with otoliths from red porgy that were smaller than 

 those available from the fisheries (n=59) and an additional 

 62 samples ranging from 300 to 425 mm total length. These 

 fish were caught primarily with Chevron traps off South 

 Carolina during 1996 and 1997. Total length, whole weight, 

 port of landing, and date of capture were recorded for each 

 sample. Tlie otoliths were stored dry in coin envelopes. 



For age analysis, three transverse (dorsoventral) sec- 

 tions from the left otolith of each fish were taken by us- 

 ing a low-speed saw. One section was made on either 

 side of the core, and the other encompassed the core. The 

 sections were mounted on glass slides with thermal ce- 

 ment, and examined through a microscope at 80x and 

 illuminated with reflected light. Clove oil was applied 

 to each section to enhance the legibility of the growth 

 zones on the section. The samples were put in sequential 

 order from smallest to largest, and one reader counted 

 the number of opaque zones in the otolith section. A sec- 

 ond reader examined a random sample of the otoliths. If 

 the readers disagreed on the age of a sample, they exam- 

 ined it again. If consensus was reached, the sample was 

 retained; otherwise, the sample was discarded. Measure- 

 ments from the core to the outer edge of each successive 

 opaque zone and the otolith margin were taken along the 

 lateral plane on the dorsal lobe of the section by using an 

 ocular micrometer. 



Analysis of the marginal increment (the distance be- 

 tween the last opaque zone and otolith margin) was used 

 to validate the annual deposition of the opaque zones in 

 the otoliths. For each age and month, the mean of the rela- 

 tive marginal increment, the ratio of the marginal incre- 

 ment to the distance between the last two opaque zones, 

 was plotted. An opaque zone was considered an annulus if 

 a minimum ratio was recorded for one month or season. 



The relationship of fish length and otolith radius was 

 described by regi'essing the obsei-ved total length on oto- 

 lith radius (/?(.). The linear equation was 



L = a +blR^.). 



where L = total length in mm. 



6 Potts, J. C, M. L. Burton, and C. S. Manooch, III. 1998. Trends 

 in catch data and estimated static SPR values for fifteen spe- 

 cies of reef fish landed along the southeastern United States. 

 Unpubl. data. South Atlantic Fishery Management Council, 1 

 Southpark Circle, Charleston, SC 29417. 



The back-calculated total lengths at each age were deter- 

 mined from the body proportional equation (Francis, 

 1990): 



L^ =[(a+hR^)/{a + bRc)]Lc, 



