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Global Status of Billfish

 

Atlantic Ocean

Marlin, sailfish, spearfish and tunas and other tuna-like species in international waters of the Atlantic are under the jurisdiction of the International Commission for the Conservation of Atlantic Tuna (ICCAT). Scientists frequently use the term “overfishing” to describe the situation where a stock is being fished at a higher rate than can be sustained. Similarly, the term “overfished” refers to where a stock has been reduced to below a targeted management level. Currently, Blue marlin are overfished and overfishing is still occurring with the stock at roughly 39% of the biomass that would produce maximum sustainable yield (MSY).[1] White marlin are overfished and overfishing is continuing[2] with the stock currently at less than 25% of the biomass that would sustain MSY. Attempts to do quantitative assessments on sailfish have not been successful due to lack of accurate catch and effort data from all harvesters, but trends in catch-per-unit-effort – an indicator of stock abundance – have fallen consistently since the 1970s.[3] There has been no effort to attempt any assessment of the spearfish species of the Atlantic and we do not know if populations are at sustainable levels.
 
 
Pacific Ocean
International management authority in the Pacific is shared by the Inter-American Tropical Tuna Commission (IATTC) and the West and Central Pacific Fisheries Commission (WCPFC). There has never been an assessment of the status of black marlin in the Pacific, but landings trends over the past thirty years have been generally declining.  There have been contradictory results in recent assessments of Pacific blue marlin status.  A 2001 assessment by the IATTC staff [4] and a 2003 effort by collaborating scientists [5]show the stock to be fully exploited.  In contrast research done in 2002[6] to develop a broad-based estimate of pelagic ecosystem species shows that blue marlin had declined the most in abundance of any of these tuna-like species being at only 21% of their pre-1960 abundance. No conservation measures are in place for either blue marlin or black marlin on the Pacific high seas. 
 
The most recent (2007) assessment by the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific (ISC) revealed that North Pacific striped marlin have been severely reduced in abundance and the spawning potential ratio (SPR) is estimated at 9% of maximum.[7] SPR is often used as a guideline to gauge the health of a fish stock and the usual targeted levels are 20% to 40%. It is useful to note that data available for this assessment was only current through 2003. As a result of this study the ISC recommended that the RFMO with jurisdiction over this stock, the WCPFC take action to reduce fishing mortality. The WCPFC has not taken any such action,[8] and the stock continues to be overfished with no conservation measures in place.
 
There has been no effort to assess the status of sailfish or spearfish species in the Pacific. Neither the IATTC or the WCPFMC can provide accurate advice on the health of the stock and no conservation measures are in place. Recent catch-per-unit-effort data from the recreational fishery off of Central America has generated cause for concern.
 
 
Indian Ocean
 
The Indian Ocean high seas fisheries are the responsibility of the Indian Ocean tuna commission (IOTC). The Indian Ocean is home to blue marlin, black marlin, striped marlin and sailfish. Although fishing pressure on tunas has increased dramatically in recent years [9] and tuna catches have dropped precipitously over the last two years[10] there is no assessment and little useable data available to determine the health of marlin populations.[11],[12]   The IOTC cannot advise on the status of these billfish species and no conservation measures are in place. 
 
 
Summary
There has been a general lack of responsible action to protect billfish species across all the world’s regional fisheries management organizations (RFMOs). For the four stocks with existing scientific status assessments, two are severely overfished (Atlantic blue and white marlin) and two (Pacific striped and blue marlin) are either fully exploited or overfished with contrary results in the published literature. Of even more concern is the lack of any determination of status for most stocks and the indifference of the RFMOs to correcting this situation.   
 
 



[1] Billfish Assessment Meeting. Report of the 2006 ICCAT Billfish Stock Assesent. Madrid, May 15-19. SCI-012/2006.   http://www.iccat.int/Documents/SCRS/DetRep/DET_bil.pdf
 
[2] ibid.
 
[3] Report of the 2001 Billfish Species Group Session . Madrid Oct. 1-7, 2001. ICCAT SCRS. http://www.iccat.int/Documents/SCRS/DetRep/DET_sai.pdf
 
[4] Status of blue marlin in the Pacific Ocean. Inter-American Tropical Tuna Commmission. , 285-319."  Hinton, M.G.  2001  Stock Assessment Report 1  IATTC 
 
[5] "Stock assessment of blue marlin (Makaira nigricans) in the Pacific using MULTIFAN-CL."  Kleiber, P., M.G. Hinton, and Y. Uozumi  2003  Marine & Freshwater Research, 54(4): 349-360.
 
[6] Cox, Sean P., et al. Reconstructing ecosystem dynamics in the central Pacific Ocean, 1952–1998. I. Estimating population biomass and recruitment of tunas and billfishes. Canadian Journal of Fisheries and Aquatic Science. 59(11).
 
[7] Report of the Seventh Meeting of the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific. July 25-30, 2007. Busan, Korea.
http://isc.ac.affrc.go.jp/isc7/ISC7_Plenary_Report-FINAL.pdf
 
[8] Discussion Paper for the Inclusion of   Northern Striped Marlin on the Northern Committee Species List.    Prepared by the Secretariat. WCPFC-SC3/GN WP-3. 2007.   http://www.wcpfc.int/sc3/pdf/WCPFC-SC3%20GN%20WP-3%20Northern%20striped%20marlin_rev%201.pdf
 
[9] Report of the ninth session of the scientific committee of the IOTC. 2006.
http://www.iotc.org/files/proceedings/2006/sc/IOTC-2006-SC-R[EN].pdf
 
[10] http://planetark.org/dailynewsstory.cfm/newsid/49652/story.htm
 
[11] Report of the ninth session of the scientific committee of the IOTC. 2006.
 
[12] Indian Ocean tuna commission working Party on Billfish. 2007.
http://www.iotc.org/files/proceedings/2008/wpb/IOTC-2008-WPB-07.pdf
 
National Coalition for Marine ConservationInternational Game Fish Association