FEATURE ARTICLE 3 

 STATUS REVIEW OF KING MACKEREL IN THE GULF OF MEXICO 



Fishery Management Plan in 1985. The goal ol 

 management is to achieve maximum sustainable 

 yield (MSY), the largest catch which can consis- 

 tently be taken from the population while prevent- 

 ing the stock from collapsing. The Gulf of Mexico 

 Fishery Management Council sets the TAG for the 

 Gulf of" Mexico group ol king mackerel as well as 

 determines the allocations amongst user groups 

 and specific regulations such as minimum size and 

 bag limits. The TAG is based upon a specihc fish- 

 ing mortality rate criteria chosen by the Gouncil. 

 The Stock Assessment Panel provides the scien- 

 tific advice on the catches that will achieve the 

 target fishing mortalitv rate in the term of a range 

 of acceptable biological catches reflecting uncer- 

 tainty in the level of catch that will achieve the 

 target fishing mortalin,' rate. The range of accept- 

 able biological catch is determined by a popula- 

 tion analysis using a mixed Monte Garlo/boot- 

 strap' algorithm that incorporates uncertainty 

 about a number of important life-historv param- 

 eters and catch statistics (Legault et al., 1998). The 

 Stock Assessment Panel recommends a specific 

 level of catch from within this range, traditionally 

 the risk-neutral median of the range. The Goim- 

 cil also incorporates recommendations from the 

 Socioeconomic Panel and angler anecdotes when 

 setting the TAG. For management purposes, the 

 fishing year for the TAG is defined as beginning 

 on 1 luly and ending on 30 June of the following 

 calendar year. 



Originallv, the TAG was set according to an 

 F|| |- strategy to achieve the goal of MSY. Imple- 

 mentation of the 6f)2 Guidelines (§50 GFR Part 

 602 guidelines for the preparation of fishery man- 

 agement plans) in l')91 required a definition of 

 the act of overfishing and a measure of overfished 

 status. The spawning potential ratio (SPR), the 

 ratio between the number of progeny that would 

 be produced under current fishing levels to that 

 which would have occurred in a virgin popula- 

 tion, was chosen as this measure. The manner in 



'Monte Carlo and bootstrap arc two resampling schemes used 

 to estimate uncertainty in the results. The rcsamplinti is done 

 from an assumed distribution (Monte Carlo) or trom the 

 oriwina! data (bootstrap). 



-At Fj, ,. only a 10% increase in yield per recruit occurs fol- 

 lowing an additional unit of fishing effort (See Appendix 4). 



which the spawning potential ratio has been cal- 

 culated, as well as a number of important life his- 

 tory parameters, such as the natural mortality rate, 

 have changed over time. The model-tuning indi- 

 ces used in the assessments have changed over time 

 as well. However, king mackerel of the Gulf of 

 Mexico Group have generallv remained classified 

 as overfished, but improving, since 1991. Gur- 

 rently, an unweighted SPR of 30% is both the tar- 

 get of management and the threshold for over- 

 fishing, a conflict which should be resolved due 

 to the implementation of new Federal guidelines 

 on definitions of overfishing. 



Management of the directed fisheries for king 

 mackerel in the Gulf of Mexico has been success- 

 ful in reducing the average fishing mortahty rate 

 and increasing the biomass (Figures 1 and 2) 

 (MSAP, 1998). These changes have occurred even 

 with a general increasing trend in catch and ac- 

 ceptable biological catch since 1987. Thus, man- 

 agement has improved the biomass level while also 

 increasing the fishery yield. This has been possible 

 due to regulations on minimum size of fish al- 

 lowed to be kept, gear types, and closed fishing 

 seasons, as well as some years of increased recruit- 

 ment. However, the goal of recovering the stock 

 from an overfished condition has not yet been ac- 

 complished. 



The Gouncil has always been risk-prone in its 

 TAG selection, choosing from the upper end of 

 the range of acceptable biological catch provided 

 by the Stock Assessment Panel. Furthermore, the 

 TAG allocations have been overrun every year, 

 slowing the recovery from an overfished condi- 

 tion. I hese allocation overruns have occurred in 

 both the recreational and commercial fisheries, but 

 have been larger both in percentage and amount 

 offish in the recreational fishery. The commercial 

 fisher\' is monitored closely during the fishing sea- 

 son through a trip ticket reporting system, and 

 each portion ot the commercial fishery is closed 

 once its quota is filled. 1 he recreational fishery is 

 monitored through the Marine Recreational Fish- 

 eries Scientific Survey (MRFSS'), which provides 

 estimates of recreational catches in 2-month 

 blocks. Bao limits and minimum size regulations 



'NMHS Fisheries St.itistics and Economics Division. Office 

 of Science and Technology, Silver Spring. MD 20910. 



8 3 



