SCRS/2009/047 Collect. Vol. Sci. Pap. ICCAT, 65(5): 1692-1700 (2010)

UPDATED U.S. CONVENTIONAL TAGGING DATABASE FOR ATLANTIC (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 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 , 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 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 (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 , 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 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 include: bluefin tuna, blue ( nigricans), ( 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

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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 release and recapture studies of billfish tagging programs reported in previous ICCAT working documents have differed little from the current report (Bayley and Prince, 1994; Jones and Prince, 1998; Prince et al., 2001). Billfish recapture rates have been historically low (<2%) and consistently less than the other target species. Ortiz et al. (2003) presented possible reasons for low billfish recapture rates, including tag shedding, non-reporting, multi-national language barriers, and communication barriers between multiple user groups interacting with these species.

Given the large number of sailfish tag releases spanning a 54 year period and the associated recapture histories showing no trans-Atlantic or trans-equatorial movement, we feel these results strongly support the assumption that sailfish have a preference for coastal habitat. In addition, our tagging results suggest that the sailfish residing in the western North Atlantic mix minimally with those found in the eastern and southern Atlantic. The fact that many of the mid-Atlantic release location records proved erroneous further supports these views.

The initial analyses for defining Atlantic sailfish stock structure, for the purpose of conducting assessments, were first undertaken at the Second ICCAT Billfish Workshop in Miami, Florida, in 1992 (ICCAT 1994). At this meeting, the billfish working group examined three kinds of data for this purpose: genetic analyses (Graves and McDowell, 1994), tagging data (Bayley and Prince, 1994), and average size of the landings in the western and eastern Atlantic (Anon. 1994). There were no indications of multiple genetic stock structures, and no tag- recapture evidence indicating trans-Atlantic or trans-equatorial movements. However, there were differences in the average size of the landings between the western and eastern Atlantic. The average size (lower jaw-fork length, LJFL, cm) of eastern Atlantic sailfish was 183.9 cm LJFL, and 163.9 cm LJFL for the western Atlantic (Anon. 1994; Prince and Goodyear, 2006). The size structure data base consisted of thousands of landing measurements taken over more than forty years from each area. These differences were highly significant and these results, in addition to the other sources of information, influenced the billfish working group to agree on an East-West stock structure hypothesis at that time. The fact the sailfish were, on average, a lot larger in the eastern Atlantic was well known from previous studies (Beardsley, 1980) that speculated genetic differences could account for the disparity in sizes between eastern and western Atlantic areas. However, a later report by Graves and McDowell (1994) could not substantiate any genetic differences within the Atlantic (for the biomarkers tested). Insights into what may cause the eastern Atlantic sailfish to attain a larger size did not become apparent until Prince and Goodyear (2006) reported that hypoxia-based habitat compression for fishes in the eastern tropical Pacific may increase foraging opportunities for pelagic species. Potentially, the same phenomenon exists in the eastern tropical Atlantic because of similar oceanographic features that result in hypoxia-based habitat compression (Prince and Goodyear, 2006).

5. Concluding remarks

1. A total of 261,787 blue marlin, white marlin, sailfish, swordfish, bluefin tuna, and yellowfin have been tagged in the CTC and TBF constituent-based conventional tagging programs in the Atlantic since 1954;

2. More than 92,201 Atlantic sailfish have been tagged by the CTC/TBF programs, nearly double the number of any other target species;

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3. Sailfish rank second only to bluefin tuna (which has an intense commercial fishery) in terms of the total number of recaptures (1,896). Sailfish have the highest recapture rate (2.05%) of any of the istiophorid billfish;

4. Many of the mid-Atlantic sailfish tag release locations have been shown to be erroneous due to recording errors;

5. Sailfish are the only major target species in CTC/TBF tagging programs that has not produced any documented transatlantic or trans-equatorial movements;

6. Given these facts, we feel that sailfish have a greater affinity for coastal areas than the other highly migratory species targeted in the tagging programs, and that sailfish in the western North Atlantic mix minimally with those in the eastern and southern Atlantic;

7. The protocols used previously (Anon. 1994) for defining Atlantic sailfish stock structure (i.e., East/West hypothesis), included genetic analyses, tagging data, and average size of landings as the main factors of consideration. If alternative stock structure scenarios are to be considered by the working group, then these same factors (along with any new data sources) should be included for the purpose of consistency.

References

Anon. 1994. Report of the Second ICCAT Billfish Workshop. Collect. Vol. Sci. Pap. ICCAT, 41: 13-166.

Bayley, R.E. and Prince, E.D. 1994, Billfish tag-recapture rates in the western Atlantic and the ICCAT billfish tagging program. Collect. Vol. Sci. Pap. ICCAT, 42: 362-368.

Beardsley, G.L. 1980, Size and possible origin of sailfish, Istiophorus platypterus, from the eastern Atlantic Ocean. Fish. Bull., 78: 805-808.

Graves, J.E. and McDowell, J.R. 1994, Genetic analysis of billfish population structure. Report of the Second ICCAT Billfish Workshop. Collect. Vol. Sci. Pap. ICCAT, 41: 505-515.

Jones, C.D. and Prince, E.D. 1998, The cooperative tagging center mark-release database for Istiophoridae (1954-1995). Collect. Vol. Sci. Pap. ICCAT, 47: 311-322.

Ortiz, M., Prince, E.D., Serafy, J.E., Holts, D.B., Davy, K.B., Pepperell, J.G., Lowry, M.B. and Holdsworth, J.C. 2003, Global overview of the major constituent-based billfish tagging programs and their results since 1954. Mar. Fresh. Res., 54: 489-507.

Orbesen, E.S., Hoolihan, J.P., Serafy, J.E., Snodgrass, D., Peel, E.M. and Prince, E.D. 2008, Transboundary movement of Atlantic istiophorid billfishes among international and U.S. domestic management areas inferred from mark-recapture studies. Mar. Fish. Rev., 70(1): 14-23.

Prince, E.D., Ortiz, M.A., Rosenthal, D, Venizelos, A. and Davy, K. 2001, An update of the tag release and recapture files for Atlantic Istiophoridae. Collect. Vol. Sci. Pap. ICCAT, 53: 198-204.

Prince, E.D., Ortiz, M., Venizelos, A. and Rosenthal, D.S. 2002, In-water conventional tagging techniques developed by the cooperative tagging center for large, highly migratory species. Am. Fish. Soc. Symp. 30: 155-171.

Scott, E.L., Prince, E.D. and Goodyear, C.P. 1990, History of the cooperative game fish tagging program in the Atlantic Ocean. Am. Fish. Soc. Symp., 7: 841-853.

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Table 1. Conventional tag releases, total recaptures, recapture percentage (RECAP %), number trans-Atlantic recaptures, and percent trans-Atlantic recaptures of main target species from the Cooperative Tagging Center (CTC) and The Billfish Foundation (TBF) constituent-based tagging programs. CTC data are from 1954-2008 and TBF data are from 1990-2008.

Number Percent Number Total Percent Species trans-Atlantic trans-Atlantic Releases Recaptures recaptures recaptures recaptures Sailfish 92201 1896 2.06 0 0.00 Blue marlin 51762 791 1.53 22 2.78 White marlin 49013 976 1.99 6 0.61 Bluefin tuna 46060 4759 10.33 229 4.81 Swordfish 12373 446 3.60 5 1.12 Yellowfin tuna 10378 439 4.23 44 10.02

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Figure 1. a) Atlantic sailfish conventional tag releases from the Cooperative Tagging Center (CTC, 1955-2008) and The Billfish Foundation (TBF, 1990-2008) tagging programs. Release points in the mid-Atlantic were examined for location errors as these data were considered suspect due to the propensity of this species to be more coastal in distribution. Black circles indicate sailfish release locations, plus signs indicate erroneous locations, triangles indicate verified correct data, and stars indicate those data that could not yet be verified. b) Atlantic sailfish conventional tag releases (black circles) from the CTC and TBF with erroneous points removed.

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Figure 2. Atlantic sailfish conventional tag recapture displacements from the composite CTC and TBF data base (CTC 1955-2008, TBF 1990-2008).

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Figure 3. Atlantic sailfish release and recapture data by month for the Florida East coast (1955-2006). Figure used by permission of Orbesen et al. (2008).

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Figure 4. Conventional tagging results (1955-2005) for Atlantic sailfish, white marlin, and blue marlin showing distance moved (km) versus years at-large. Figure used by permission of Orbesen et al. (2008).

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