Catch and bycatch of gag grouper in the Gulf of Mexico shark and reeffish bottom longline fishery based on observer data Simon J.B. Gulak and John K. Carlson SEDAR33-DW23 20 May 2013 This information is distributed solely for the purpose of peer review. It does not represent and should not be construed to represent any agency determination or policy. Please cite as: Gulak, S.J.B. and J.K. Carlson. 2013. Catch and bycatch of gag grouper in the Gulf of Mexico shark and reeffish bottom longline fishery based on observer data. SEDAR33-DW23. SEDAR, North Charleston, SC. 28 pp. SEDAR33-DW23 Catch and bycatch of gag grouper in the Gulf of Mexico shark and reeffish bottom longline fishery based on observer data Simon J.B. Gulak John K. Carlson National Marine Fisheries Service Southeast Fisheries Science Center-Panama City Labortory 3500 Delwood Beach Rd Panama City, FL Introduction In the Gulf of Mexico, two fisheries utilize bottom longline gear to harvest Federally managed species. The shark bottom longline fishery currently has about 100 active vessels in the south Atlantic and Gulf of Mexico out of about 218 vessels that possess directed shark fishing permits. Depending on regulations, commercial shark fishers target and land sandbar shark, Carcharhinus plumbeus, blacktip shark, Carcharhinus limbatus, bull shark, Carcharhinus leucas and hammerhead sharks , Sphyrna spp. The commercial reef fish involves about 819 permitted vessels that target groupers, snappers, and other reef fish species with approximately 130 vessels reported using bottom longline gear. Details of the shark bottom longline fishery and its operations can be found in Hale et al. (2012 and reference therein) and for the reeffish fishery in Scott-Denton et al. (2011). Data collected by the NMFS-Panama City Laboratory in the shark bottom longline fishery by on-board observers began in 2005 (Hale and Carlson, 2007). Regardless of the target species, if a vessel was selected during the coverage period it was required to carry an observer. Thus, while the focus of the observer program was on shark directed trips, observers also boarded bottom longline fishing trips that targeted 1 grouper, snapper, and tilefish as well as shark. Because of the overlap observed in 2005 with grouper/snapper targeted longline sets and those vessels possessing directed shark permits (some vessels hold both shark and reeffish permits), the vessel pool covered all bottom longline vessels regardless if they reported fishing for sharks with bottom longline gear. The objectives are to report observations on the catch and bycatch of gag grouper, Mycteroperca microlepis, in Gulf of Mexico shark and reeffish targeted bottom longline sets from 2005–2012. Methods Vessel selection NMFS observers were placed on bottom longline vessel targeting shark or reeffish throughout the Gulf of Mexico based season and region. Observer coverage is based on proportional sampling effort, based on coastal logbook data, among seasons in the Gulf of Mexico. Selection letters requiring observer coverage were issued to permit holders via U.S. certified mail approximately one month prior to the upcoming season. Once the permit holder received the selection letter, he or she was required to contact the observer coordinator and indicate intent to fish during the upcoming fishing season. If the permit holder intended to fish, the observer coordinator deployed an observer to the port of departure (Hale et al. 2012). 2 Observer Protocol For consistency among longline observer programs throughout the Southeast Fisheries Science Center, observers complete three data forms: Longline Gear Characteristic Log, Longline Haul Log, and Individual Animal Log. The Longline Gear Characteristic Log is used to record the type and length of the mainline used, number and length of gangions, and make and model of hooks used. The Longline Haul Log is used to record the length, location, and time duration for each set and haulback, as well as environmental information and the type(s) of bait used. The Individual Animal Log records all species caught, condition on capture (e.g. alive, dead, damaged, or unknown) when brought to the vessel, and the final condition on release (e.g. kept, released, finned, etc.). When an animal is brought aboard the vessel, the observer records species, condition on capture, sex (when possible), and length. Results and Discussion Observer coverage summary A total of 332 trips on 61 vessels (2217 sets) were observed in the Gulf of Mexico region from July of 2005 through December of 2012 (Figure 1). All sets utilized bottom longline gear with 76.7% (1699 sets) targeting reef fish (grouper, snapper), 21.0% (466 sets) targeting shark, 1.5% (33 sets) targeting tilefish, 0.6% (14 sets) targeting mixed species (shark and reef fish within the same set) and 0.2% (5 sets) targeting eel for bait. Due to low sample sizes, sets targeting tilefish, mixed species or bait are not described here in further detail. More in-depth catch information is reported in a yearly technical memorandum from the observer program (eg. Hale et al. 2012 and references therein). A 3 total of 37 vessels were observed on 73 trips (average trip length was 11.7 days with an average of 25.8 sets per trip) targeting reef fish, while a total of 30 vessels were observed on 263 trips (average trip length was 2.0 days with an average of 2.4 sets per trip) targeting shark. Based on Richards (2008), the percent observed of the total reef fish bottom longline effort was 0.75-2.1% for 2006-2007. Some vessels targeted different species on different trips within the same year or between years. Of the 2217 sets observed (all targets combined), 638 sets (28.8%) caught gag grouper. 4 Gear description In shark-targeted sets, the length of the mainline ranged from 0.4 – 35.2 km with an average length of 12.1 km (±7.8 Standard Deviation (S.D.)). Number of hooks set ranged from 25 - 1354, with an average of 390 hooks (±280 S.D.) per set. Depth ranged from 2 - 227 m with an average depth of 48.8 m (±34.8 S.D.). The gear was soaked an average of 12.9 hrs (±9.1 S.D.). The majority of longline vessels utilized circle hooks (80.7%). Some sets (14.3%) used two different hooks with 4.3% using a combination of circle and J-hooks. The most commonly used hooks were 18.0 and 16.0 circle hooks (51.5% and 24.3% respectively). Total hook effort was 181,631 hooks while total hook hours were 2,272,436.2 hours. In reef fish-targeted sets, the length of the mainline ranged from 0.7 – 25.2 km with an average length of 9.1 km (±3.6 S.D.). Number of hooks ranged from 30 - 2300, with an average of 766 hooks (±352 S.D.) per set. Depth ranged from 29 - 355 m with an average depth of 98.8 m (±68.0 S.D.). The gear was soaked an average of 1.6 hrs (±2.4 S.D.). Reef fish vessels utilized circle hooks 98.7% of the time, and a combination of circle hooks sizes in 30.9% of sets. The most commonly used hooks were 13.0 and 14.0 circle hooks (46.7% and 32.1% respectively). Total hook effort was 1,301,478 hooks while total hook hours were 2,037,347.3 hours. Observed Gulf of Mexico catches Total observed catch composition (percent of numbers caught) of trips targeting shark was 95.4% sharks, 3.8% teleosts, 0.3% batoids, and 0.4% invertebrates, and 0.2% protected resource species (Table 1). Sandbar shark, Carcharhinus plumbeus, and 5 blacktip shark, Carcharhinus limbatus, were the most common species caught (28.1% and 19.2% by number respectively). Gag grouper made up 2.4% by number of the teleost species (n = 21). The catch per unit effort (CPUE) for gag grouper was 0.11 per 1000 hooks. The average length of gag grouper caught was 88.3 cm fork length (n = 19). The 91 to 100 cm FL categories had the highest percentage of individuals (42.1%, Table 3). Of the gag grouper, 5.3% were undersized according to current regulations (less than 22 inches or 55.9 cm TL; Gulf of Mexico Fishery Management Council, 2012). Total observed catch composition (percent of numbers caught) of trips targeting reef fish was 7.6% sharks, 91.8% teleosts, 0.1% batoids, 0.5% invertebrates, and <0.1% protected resource species (Table 2). The most commonly caught species was the red grouper, Epinephelus morio, (58.1% by number, n = 60,916) and Atlantic sharpnose shark, Rhizoprionodon terraenovae, was the most common shark species (34.6% by number of overall shark species). Gag grouper made up 1.7% by number of the overall teleost species (n = 1622. The CPUE for gag grouper was 1.25 per 1000 hooks. The average length of gag grouper caught was 80.4 cm fork length (Tables 3 & 4, Figure 2). The 71 to 80 cm FL category had the highest percentage of individuals (33.6%). Of the gag grouper, 1.9% were undersized according to current regulations (less than 22 inches or 55.9 cm TL; Gulf of Mexico Fishery Management Council, 2012). 6 Observed depth range of gag grouper catch The depth of shark-targeted sets that caught gag grouper ranged between 10 - 121 m with an average depth of 66.1 m. Gag grouper were commonly caught between two depth categories (Table 5): 51-60 (23.8%) and 81-90 m (23.8%). The depth of reef fish- targeted sets that caught gag grouper ranged between 29 - 238 m with an average depth of 71.5 m.