Section 3. Distribution 



Summer Concentration of White Marlin, Tetrapturus albidus, 



West of the Strait of Gibraltar 1 



C. RICHARD ROBINS 2 



ABSTRACT 



Examination of fish catches landed in August 1961 at various ports in southern Portugal and the 

 adjacent coast of Spain demonstrated that the white marlin. Tetrapturus albidus, concentrated in these 

 waters during this month. The coincident absence of white marlin in landings at Sicily make it likely that 

 the species does not enter the Mediterranean in any numbers at least at this season. 



August concentrations of white marlin elsew here in the Atlantic are discussed along with the implica- 

 tions of the coincident timing of them on population structure of the species. 



Morphometric data are presented on 57 specimens from this eastern Atlantic population to facilitate 

 future comparison with specimens from elsewhere in the range of the species. 



In 1961. the writer visited Italy. Spain, and Por- 

 tugal to study 95 istiophorid fishes that had been 

 purchased from fishermen and stored in large freez- 

 ers for that purpose. Arrangements for the purchase 

 and storage of the fish had been made by the late 

 John K. Howard during his travels through the re- 

 gion in the summers of 1960 and 1961. 



The main goal of the project was to determine the 

 status of the Mediterranean spearfish. Tetrapturus 

 belone Rafinesque. and that result was published by 

 Robins and de Sylva (1963) based on thirty-five 

 specimens, all from Sicily. Equal attention, how- 

 ever, was devoted to other istiophorids. Of the re- 

 maining 60 specimens, 57 were white marlin, Tet- 

 rapturus albidus Poey. an amphi- Atlantic species 

 whose biology remains poorly known. 



Except for three specimens, one caught 14 Sep- 

 tember, and two on 5 October, all specimens were 

 collected between 31 July and 24 August 1961 off 

 the southern coasts of Portugal and Spain and off 

 northwestern Morocco. The 1961 season was said 

 to be especially good off Olhao. Portugal. The 

 species is said to be especially common in this re- 

 gion in August, which coincides with the time of 



Contribution No. 1710 from the Rosenstiel School of Marine 

 and Atmospheric Science. University of Miami. 



Rosenstiel School of Marine and Atmospheric Science. 

 Universirv of Miami. Miami. FL 33149. 



postspawnirtg feeding concentrations elsewhere. 

 Between Ocean City, Maryland and Atlantic City, 

 New Jersey, the peak season extends from the end 

 of the second week of July to about the last week in 

 August (de Sylva and Davis, 1963: tables 2 and 3); 

 off the Mississippi Delta, in the Gulf of Mexico a 

 large concentration occurs in July and August 

 (Gibbs. 1958: Figure 1); and off La Guaira, Ven- 

 ezuela, the peak is also in August but large numbers 

 occur through September and into October (Perez 

 de Armas. 1959. and unpublished data courtesy of 

 Donald P. de Sylva). 



With four, nearly simultaneous, postspawning 

 concentrations known to occur in distant parts of 

 the Atlantic Ocean, the population structure of this 

 giant pelagic predator obviously is complex. 

 Mather (1968) discusses the results of a tagging 

 program in the western Atlantic which had then 

 yielded 34 returns out of nearly 4,000 tagged fish. 

 He comments on the three western Atlantic popula- 

 tions which he terms the northwestern Atlantic 

 stock. Gulf stock, and Venezuelan stock. To facili- 

 tate morphometric comparison of the populations, 

 and because these large fishes are not preserved 

 and thus are unavailable to future researchers, the 

 data obtained from the eastern Atlantic specimens 

 are presented here following the format of Robins 

 and de Sylva (1961, 1963). Certain aspects of the 

 biology are discussed. 



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