Evaluation of Identification Methods 

 For Young Billfishes 1 



WILLIAM J. RICHARDS 2 



ABSTRACT 



Most of the papers published from 1831 to date which deal with the identification of young billfishes 

 (Families Xiphiidae and Istiophoridae) are reviewed. The present knowledge of the identification of adults is 

 compared with the identification of young and problem areas are defined. Suggestions are made to resolve 

 the present problems encountered with the identification of the young stages (eggs, larvae, and juveniles). 

 These suggestions include the need for detailed osteological descriptions of the young, the need for an 

 increased effort to collect specimens, and the need to artificially rear specimens in the laboratory. 



The purpose of this paper is to review the identifi- 

 cation work that has been done on young billfishes 

 over the years, to summarize the present methods 

 used for identifying young billfishes, and to evaluate 

 the identification methods. 



Knowledge of the young stages of fishes is useful 

 for determining spawning areas and times, and for 

 estimation of sizes of adult spawning stocks. 

 Prerequisite to this knowledge is the ability to iden- 

 tify the young stages of the species in question 

 — from eggs through larvae to juveniles. 



Currently, there are two methods available to us 

 to make these identifications. Both methods require 

 a complete series of specimens which will show all 

 the different stages of development plus the indi- 

 vidual variations which may be found in a particular 

 species. 



The first method is to artificially fertilize eggs, 

 then rear the products in the laboratory. This tech- 

 nique provides an ideal series of specimens with the 

 only limitations being anomalies resulting from rear- 

 ing under artificial conditions, and the possibility 

 that your material is influenced by a limited number 

 of parents. Both limitations can be circumvented by 

 comparing reared specimens with specimens caught 

 in the wild. Wild caught eggs can be collected and 

 brought into the laboratory and reared, thus avoiding 

 the difficulties of catching ripe fish or by maturing 



'Contribution No. 228. National Marine Fisheries Service. 

 Southeast Fisheries Center. Miami Laboratory. Miami. FL 

 33149. 



2 NOAA, National Marine Fisheries Service. Southeast 

 Fisheries Center. Miami Laboratory. Miami. FL 33149. 



gonads artificially. This method has been used suc- 

 cessfully for very early stages of billfishes (Sanzo, 

 1922). 



The second method is to collect a large series of 

 specimens in the field over a wide enough size range 

 so that one can work backwards from the adult, 

 utilizing characters common to the adults, then to 

 juveniles, larvae, and eggs. This approach requires 

 that enough specimens be collected to develop suffi- 

 cient series so that all the necessary characters will 

 be available. The problems inherent in the rearing 

 method are not relevant to this method, particularly 

 when the material is from a wide geographic range, 

 preferably the entire spawning range of the species. 

 The prerequisite for the taxonomic approach is a 

 firm knowledge of the adults. Unfortunately, some 

 adult taxonomic problems still exist and the first 

 section briefly summarizes these problems. 



IDENTIFICATION STATUS 

 OF ADULTS 



Nakamura, Iwai, and Matsubara (1968) com- 

 pleted the most recent review of the billfishes of the 

 world. They recognized 11 species in two families, 

 Xiphiidae and Istiophoridae; the former monotypic, 

 the latter with 10 species in three genera. These 

 species, their English and Japanese names, and their 

 distributions are: 



Xiphias gladius Linnaeus, 1758. Swordfish, 

 Mekajiki. Cosmopolitan. 



Istiophorus platypterus (Shaw and Nodder, 1792). 

 Pacific sailfish, Bashokajiki. Indo-Pacific Ocean. 



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