Fishery Bulletin 103(1) 



discards from demersal trawlers operating in certain 

 areas and depths in the Mid-Atlantic Bight. High num- 

 bers of scup discards occur in the directed scup fishery 

 (Powell et al., 2004). It is generally believed that one of 

 the keys to effective management of scup is to reduce 

 discard mortality (NEFSC 2 ; NEFSC 1 ). Fisheries manag- 

 ers attempt to control discard mortality using a number 

 of management measures, but principally through mesh 

 regulations and time or area closures. 



Analysis of NMFS observer data by Powell et al. 3 

 indicated that scup comprised 65% of the total catch in 

 scup-targeted tows, but that the discards-to-landings 

 ratio for scup in these tows was 1.05. Somewhat more 

 than half of the scup taken in scup-targeted tows were 

 subsequently discarded. However, this analysis was 

 based on relatively few observations; many of the tows 

 used codends with mesh sizes below the current legal 

 mesh size of 11.43 cm. As a consequence, applicability 

 of the NMFS observer data to the present-day scup 

 fishery is unclear. The objective of the present study 

 was to obtain additional observations in the directed 

 scup fishery to re-assess the level of discards by weight 

 and to evaluate the effect of simple variations in codend 

 mesh size on the level of scup discards. 



Data analysis focused on scup. However, we also ana- 

 lyzed black sea bass (Centropristis striata) catches using 

 the same methods as those for scup. Black sea bass 

 were included because one management option is to 

 require a common codend mesh size for the two spe- 

 cies. The present legal mesh size for black sea bass is 

 10.16 cm and the minimum size of black sea bass that 

 can be harvested is 27.94 cm TL. Commonality would 

 simplify fishing methods because the two species are 

 often targeted on the same trip. 



Methods 



Description of data 



This study was undertaken during the 2001 winter scup 

 trawl fishery in the Mid-Atlantic Bight. The legal trip 

 limit for scup was 4536 kg from 1 January through 24 

 January. After 24 January until the close of the season 

 in late February, the legal trip limit for scup was lowered 

 to 454 kg. An experimental fishing permit was obtained 

 from NMFS 1) to allow the vessels to fish in the GRAs 

 (gear-restricted areas), implemented to reduce scup 

 discards in the Loligo squid, (Lollgo pealei), silver hake 

 (Merluccius bilinearis), and black sea bass fisheries, 2) 

 to allow the use of codends with meshes less than the 

 legal 11.43-cm mesh, and 3) to allow commercial vessels 



to retain an additional 1361 kg of scup per trip to help 

 defray study costs. 



The four vessels participating in this study used the 

 following codends: 1) the legal-size (11.43-cm) mesh co- 

 dend; 2) a composite codend with 30 meshes of 10.16-cm 

 mesh at the very end of the bag followed by 45 meshes 

 of 11.43-cm mesh; and 3) codends with some meshes 

 212.7 cm (including codends with or without a com- 

 posite design). Two tows with codends of smaller mesh 

 size (between 6.35 and 10.16 cm) were also observed 

 and these tows were included in data tabulations for 

 completeness. The composite codend was designed as a 

 mechanism to reduce large catches of small scup when 

 abundant scup are encountered but was also designed 

 to retain black sea bass and scup when abundance was 

 low. Captains usually had two of the codends onboard 

 the vessel during a fishing trip and were asked to fish 

 the codends in an ABBA sequence (i.e., first tow with 

 codend A, second tow with codend B, third tow with 

 codend B, next tow with codend A, and so forth). These 

 tows typically lasted no longer than one hour. Other- 

 wise, the captain operated his boat using normal fishing 

 practices, including selecting where and when to fish. 



The catch from each tow was sorted to species and 

 weighed. Fork lengths (FL) were obtained for a mini- 

 mum of fifty scup discarded followed by a minimum of 

 fifty scup landed. If time permitted, length-frequency 

 information was collected for black sea bass and dis- 

 carded individuals were measured. Because some regu- 

 lations use TL, FL was converted when necessary to TL 

 with the following equation: TLtcm) = 1.14FL(cm) - 0.44 

 (Hamer 4 in MAFMC [1996]). 



Catch data obtained from this study of the winter 

 2001 scup fishery were compared to scup-targeted tows 

 from the NMFS observer database for 1997 through 

 mid-2000 (Powell et al. 3 ). NMFS observer program 

 methodology is detailed in the Northeast Fisheries 

 Science Center Fisheries Observer Program Manual 

 (NEFSC 5 ). Mesh size reported in the NMFS observer 

 database included an array of small-mesh codends less 

 than present-day legal size, as well as the legal mesh 

 size of 11.43 cm. 



A depth was assigned for each tow as the mean of the 

 depths of net deployment and retrieval. Swept area of 

 the tow could not be calculated directly because door 

 or wing spread were not recorded by us, nor were these 

 metrics available in NMFS observed tows. A surrogate 

 for true swept area was obtained as "the average of 

 the recorded headrope and sweep lengths" multiplied 



3 Powell, E. N., E. A. Bochenek, S. E. Banta, and A. J. 

 Bonner. 2000. Scup bycatch in the small-mesh fisher- 

 ies of the Mid-Atlantic. Final Report, National Fisheries 

 Institute Scientific Monitoring Committee, 74 p. Haskin 

 Shellfish Research Laboratory, Rutgers University, 6959 

 Miller Ave., Port Norris, NJ 08349. 



4 Hamer, P. E. 1979. Studies of the scup, Stenotomus chrys- 

 ops, in the Middle Atlantic Bight. N.J. Div. Fish. Game and 

 Shellfish, misc. rep. no. 5M, 14 p. New Jersey Department 

 of Environmental Protection, New Jersey Division of Fish 

 and Wildlife, Division of Marine Fisheries, Nacote Creek 

 Research Station, PO Box 418, Port Republic, NJ 08241. 



5 NEFSC (Northeast Fisheries Science Center). 2001. Fish- 

 eries observer program manual, 217 p. Northeast Fisheries 

 Science Center, NMFS, NOAA, 166 Water St., Woods Hole, 

 MA 02583. 



