SCRS/2009/047 Collect. Vol. Sci. Pap. ICCAT, 65(5): 1692-1700 (2010) UPDATED U.S. CONVENTIONAL TAGGING DATABASE FOR ATLANTIC SAILFISH (1955-2008), WITH COMMENTS ON POTENTIAL STOCK STRUCTURE Eric S. Orbesen, Derke Snodgrass, John P. Hoolihan, and Eric D. Prince1 SUMMARY The U.S. conventional tagging data base for Atlantic sailfish (1955-2008), Istiophorus platypterus, consists of data from the NOAA Southeast Fishery Science Center’s Cooperative Tagging Center (CTC) and The Billfish Foundation (TBF). We examined the patterns of sailfish tag release and recapture results in the Atlantic Ocean using a composite analysis from both agencies. In addition, we discuss tagging results and other data that might provide insight into Atlantic sailfish stock structure. RÉSUMÉ La base de données de marquage conventionnel des Etats-Unis pour les voiliers de l’Atlantique (Istiophorus platypterus) (1955-2008) est constituée de données provenant du Cooperative Tagging Center (CTC) du Southeast Fishery Science Center de la NOAA et du The Billfish Foundation (TBF). Nous avons examiné les modes des résultats d'apposition des marques sur les voiliers et de leur récupération dans l’océan Atlantique à l’aide d’une analyse composite émanant des deux agences. En outre, nous discutons des résultats de marquage et d’autres données susceptibles de nous éclairer sur la structure du stock de voiliers de l’Atlantique. RESUMEN La base de datos de marcado convencional estadounidense para el pez vela del Atlántico (1955-2008), Istiophorus platypterus, contiene datos del Cooperative Tagging Center (CTC) del Southeast Fishery Science Center de la NOAA y de The Billfish Foundation (TBF). Se han examinado los patrones de los resultados de colocación y recaptura de marcas en el Atlántico utilizando un análisis compuesto de ambas agencias. Además, se discuten los resultados de marcado y otros datos que podrían facilitar más información sobre la estructura de stock del pez vela del Atlántico. KEYWORDS Sailfish, tagging, size composition, geographical distribution, stock assessment, fishery management 1. Introduction Constituent-based conventional tagging programs have been a major source of information used to manage “rare event” pelagic fishes, such as istiophorid billfish (Ortiz et al. 2003). In many cases, having volunteers carry out tagging is the only economically viable method to tag large numbers of billfish (Ortiz et al. 2003). NOAA’s Southeast Fisheries Science Center’s (SEFSC) Cooperative Tagging Center (CTC), formally called the Cooperative Game Fish Tagging Program (CGFTP), was originated by Dr. Frank Mather III at Woods Hole Oceanographic Institute in 1954 (Scott et al. 1990). This program is a joint endeavor between scientists and fishing constituents (commercial and recreational). The program initially targeted bluefin tuna (Thunnus thynnus) in the Atlantic and adjacent waters, but quickly was expanded to include istiophorid billfish, other Atlantic tunas, and swordfish (Xiphias gladius). In 1978 the CTC program and associated activities were transferred to the SEFSC in Miami, Florida. In 1990, The Billfish Foundation (TBF) developed a similar constituent-based conventional tagging program that focuses on marlins, sailfish, swordfish, and spearfishes caught throughout the world’s oceans. The CTC and TBF programs agreed through a joint memorandum of 1 U.S. Dept of Commerce NOAA-NMFS Southeast Fisheries Science Center, Sustainable Fisheries Division. 75 Virginia Beach Dr Miami, FL 33149 US. E-mail: [email protected] 1692 understanding (1990), to operate their programs in a similar manner to facilitate future analyses. Common program protocols including similar release and recovery cards, quality control procedures, data processing, tags, and anchoring mechanisms. The combined data from these two programs represents the majority of available data on conventional tagging of istiophorid billfishes in the Atlantic Ocean. The objectives of this document are to update the available conventional tagging data for the Atlantic sailfish (Istiophorus platypterus), and summarize how this information may elucidate stock structure. 2. Materials and methods The CTC program’s format, goals, and operational protocols are described in Prince et al. (2002). The primary target species include: bluefin tuna, blue marlin (Makaira nigricans), white marlin (Tetrapturus albidus), sailfish, swordfish, and yellowfin tuna (Thunnus albacares). In contrast, TBF tagging efforts only target istiophorid billfishes and swordfish. The first tag type used by the CTC was a streamer tag affixed to a stainless steel anchor. In collaboration with TBF the CTC developed a medical grade nylon anchor which proved to have a better retention rate than the previous anchor type (Prince et al. 2002). The nylon anchor, which has been used by TBF since 1990, was adopted by the CTC in 1995. Overall, constituents of the CTC have been tagging sailfish from 1955 to the present date, and TBF from 1990 to present. Data from both programs were merged for the purpose of providing the summary statistics presented here. The release and recapture location data were plotted on a worldwide map using ArcGIS to allow for removal of non-Atlantic interactions. With constituent based tagging programs it is assumed that the majority of interactions occur in close proximity to land. Therefore, any interactions that did not occur near a land mass were identified to allow review of the actual data card and verify if the locations were recorded correctly in the data base. 3. Results A total of 261,787 individuals from the main target species were tagged and released since 1954. The summary of tag releases, recaptures, recapture percentages, trans-Atlantic recaptures, and transatlantic recapture percentages for the main target species are provided in Table 1. Sailfish account for 35% (n = 92,201) of all tagged fish in the composite CTC/TBF programs, which is nearly twice as many as any other species (Table 1). Sailfish releases resulted in 1,896 recaptures which represents a 2.05% recapture rate, the highest for billfishes (white marlin = 1.99%, blue marlin= 1.53%). The target species associated with commercial fisheries had the greatest recapture rates (bluefin tuna = 10.33%, yellowfin tuna = 4.23%, and swordfish = 3.60%). Bluefin tuna had the highest number of recaptures (4,759), followed by sailfish (1,896), white marlin (946), blue marlin (791), swordfish (446), and yellowfin tuna (439, Table 1). Despite the large number of releases and relatively high recapture rate, sailfish are the only target species in the tagging program which has not been documented making a trans-Atlantic movement. In contrast, 22 blue marlin, 6 white marlin 229 bluefin tuna, 44 yellowfin tuna, and 5 swordfish tag recaptures indicated trans-Atlantic movements (Table 1). In addition, Orbesen et al. (2008) indicated that no sailfish has been documented making a trans-equatorial movement. The greatest concentration of Atlantic sailfish conventional tag deployments occurs off South Florida, although the Gulf of Mexico and the U.S. East coast also have a substantial number of deployments (Figure 1a). The remaining Atlantic deployments are quite sparse, despite some moderate increases in tagging activities off Brazil, West Africa, Venezuela, and the Caribbean islands. Thus, it is clear that these tagging programs continue to have primarily a western North Atlantic focus. Based on the current understanding there have been sporadic sailfish deployments in the mid-Atlantic waters (Figure 1a) but the validity of these releases were suspect due to the current estimation that sailfish abundance is greatest in near-shore waters. Upon verification with the original release cards, many of these mid-Atlantic deployment locations were found to be inaccurately recorded in the data base. Although not all mid-Atlantic sailfish deployment release cards could be accessed at this time, a large proportion of these locations were found to be erroneous. Of 85 total mid-Atlantic release records reviewed, 53 had incorrect location entries, 10 were verified to be correct, and 22 remain unverified (Figure 1a). Because of these errors, the mid-Atlantic sailfish tag releases locations depicted in Figure 1a should be viewed with caution. After removing the suspect data points, the release locations shown in Figure 1b are more representative of the historical distribution of tag released sailfish from this data base. Linear displacements for tag-recaptured 1693 Atlantic sailfish are provided in Figure 2. Clearly, the of bulk recoveries demonstrates the primary focus of this program is in the western North Atlantic. Although current data does not support the theory of a single Atlantic-wide stock, sailfish have shown seasonal abundance variability. Monthly tag-recapture data for sailfish off the Florida East coast and Keys (Figure 3) shows that most of the sailfish release and recapture activities occur during the winter months, peaking in January and declining to a seasonal low in September. A comparison of displacement distances (km) versus years at-large for billfish is illustrated in Figure 4. The maximum linear distances moved were; 16,000 km for blue marlin, 6,500 km for white marlin, and 3,845 km for sailfish. The longest linear movements for all three species tended to occur at less than three years at-large. The longest period at large was recorded by a white marlin (13 yrs), followed blue marlin (12.5 yrs), and sailfish (10.9 yrs). 4. Discussion General trends in