60 



Reasons for the Bluefish Decline; Predation; Environmental Conditions 



There cannot be much doubt today about the fact that bluefish along the Atlantic coast are in 

 significant decline. The information that supports this was summarized previously. 



There is, however, no general conclusion available from the scientific community that 

 pinpoints precisely why this decline has occurred. One possible explanation is overfishing and the 

 exploitation of age-0 bluefish. Fishing mortality has exceeded the fishery management plan's 

 overfishing reference point since at least 1986, and possibly since 1982. However, because of the 

 exploitation of juvenile bluefish, simply reducing overall fishing mortality would not be sufficient 

 to halt the declining spawning stock biomass. According to the Stock Assessment Review 

 Committee forecast for 1995, even if fishing mortality was reduced from the 1993 level of F=0.45 

 to the overfishing definition of F=0.20 and recruitment was average, spawning stock biomass 

 would still decrease by 30%. However, the same forecast indicates that if fishing mortality was 

 maintained, but exploitation of age-0 bluefish was eliminated, spawning stock biomass would 

 increase by 16%. 



An alternative explanation for the stock decline, raised at Amendment 1 Scoping Meetings 

 and ASMFC Advisory Panel meetings, is that interspecific competition and multi-species 

 interactions have influenced either the abundance or availability of bluefish. Bluefish are a minor 

 prey item of bluefin tuna; and I will touch on this in a minute. However, bluefish compete with 

 striped bass and weakfish for prey, and some fishermen suggest that increasing striped bass 

 abundance has impacted bluefish populations. Because the diet preferences of adult bluefish and 

 striped bass overlap, bluefish abimdance could be affected if they are out-competed by striped bass 

 and therefore capture less prey. More likely, competition with striped bass may push bluefish 

 farther offshore and thus affect bluefish availability to fishermen. This is possible, because striped 

 bass are nearshore predators, whereas bluefish can and do venture farther out Since most 

 recreational bluefish landings are taken between and 3 miles offshore, if bluefish are indeed 

 beyond that then recreational catches in traditional areas would surely decline. This theory is 

 difficult to test, because of a lack of offshore fishery independent survey data containing bluefish 

 as well as differing opinions of fishermen. Some fishermen state that those who venture offshore 

 do not target bluefish even though they are available, while others state that charter boats have been 

 going 20 miles or more offshore and still not finding bluefish in abundance. 



DRAFT:Testimony of John H. DunnigaD April 1, 1996 



Subcommittee on Fisheries, Wildlife and Oceans page 4 



