UNIT 7 

 ATLANTIC AND GULF OF MEXICO MIGRATORY PELAGIC FISHERIES 



1981—96. King and Spanish mackerel account for 

 about 95% of all coastal pelagic species harvested 

 (Figures 7-1 and 7-2). In addition to king and 

 Spanish mackerel, Atlantic dolphiiifish and cobia 

 contributed significantly to the total recreational 

 yield ot coastal pelagics. Some cobia are inciden- 

 tally caught by commercial mackerel fishermen; 

 however, cobia are for the most part a recreationally 

 caught species. Cero are relatively unimportant and 

 are taken as bycatch in other fisheries. Cero are 

 not known to form large schools and are more 

 difficult to target individually; in general, they do 

 not contribute significantly to coastal pelagic 

 catches. 



As a group, coastal pelagics yield only about 

 68% of their long-term potential (Table 7-1), and 

 certain species are fished near or over maximum 

 production levels. The Gult king mackerel stock 

 is considered overfished because of previous 

 overexploitation and has been managed under rigid 

 rebuilding schedules since 1985. 



The mackerels have been managed recently ac- 

 cording to spawning potential ratio' (SPR). The 

 management benchmark selected for determining 

 overfishing is H,,,,, .' The 1996-97 Atlantic Span- 

 ish mackerel SPR is estimated to be 39% of the 

 maximum potential. Fishing mortality from 

 bycatch in the shrimp fishery is believed to be 

 greater than currently anticipated. Additional in- 

 formation is needed to quantity this source of mor- 

 talit)'. Gulf Spanish mackerel were removed fiom 

 overfished status in 1995 tollowing a period ot 

 regulation to rebuild the stock that began in 1 987. 

 The 1996-97 estimated SPR is 43% of the maxi- 

 mum potential for Ciulf Spanish mackerel. Cur- 

 rentlv, fishing mortality on Gult Spanish mack- 

 erel is less than F,||„ SPR, but additional intor- 

 mation is needed on the exact level of bycatch to 

 evaluate the stock status with more certainty. 



The Gulf king mackerel stock is believed to 

 have a large long-term potential yield, but the stock 

 is severely depleted. Recent average annual pro- 

 duction is at 15% of its maxinuim level, and ma- 

 jor stock reductions were due to excessive harvests 



Landings 

 (X 1,000 t) 



13 - 



12 - 



11 - 



10 - 



9 - 



8 - 



7 - 



6 - 



5 - 



4 - 



3 - 



2 - 



Landings 



Biomass 

 index (t) 



- 1 



- 0,9 



- 08 



- 07 



- 06 



- 05 



- 04 



- 03 



- 02 



Figure 7-2 



Landings and bionnass in- 

 dex in metric tons (t) of 

 Spanish mackerel, 1984-97 

 The biomass index is the es- 

 timate in weight (t), and the 

 highest year is given the 

 relative value of 1.0. 



' rhe spawning potenti.il ratio is tlie amount of reproductive 

 output for one recruit relative to tfie amount expected under 

 no fishing (see Appendix 4). F^^,,, is rhe fishing mortality 

 rate expected to produce 30% SPR. 



84 85 86 87 88 89 90 91 92 93 94 95 96 



Year 



from the late 1970's through the early 1980's. Ab- 

 sence of fishing ettort controls and sparse data 

 hampered determining stock status and conserva- 

 tion efforts until 1986. 



The Atlantic king mackerel stock is near its 

 long-term potential yield. Catches have remained 

 stable since l')81 with annual total allowable 

 catches not reached in most years. Bycatch ot At- 

 lantic king mackerel is assumed low. The 1996- 

 97 estimated SPR level is 27% ot the maximum 

 level. 



The status ot cobia and dolphintish stocks re- 

 mains uncertain. Atlantic cobia yields have ranged 

 trom 351 to 627 t since 1987. Gult cobia yields 

 are traditionally much larger than those of Atlan- 

 tic cobia. Fishing mortality is assumed to be low 

 for the Atlantic group, and Gulf cobia are believed 

 to be more heavily exploited. The 1994 SPR cal- 

 culation tor Gult cobia was about 20%. Manage- 

 ment ot cobia stocks assumes two separate stocks 

 for assessment. Cobia and dolphinfish mostly are 

 caught by recreational anglers, but data needed to 

 assess their long-term potential are limited. In ad- 

 dition, updated information is needed to investi- 

 gate the possibilit)' ot separating cobia into Gult 

 and Atlantic stocks. Also, refined estimates ot co- 

 bia bycatch, natural mortalit}' rate, and increased 

 biostatistical sampling throughout the range ot 

 cobia are needed to improve assessment of stock 

 status and accuratelv estimate long-term poten- 

 tial yields. 



1 27 



