891 



Abstract.— The age and growth of dol- 

 phin, Coryphaena hippurus. has been 

 determined in wild specimens between 

 14.4 and 124 era fork length (FL) caught 

 off Majorca (Balearic Islands, western 

 Mediterranean ). Also, several methods 

 have been applied to validate the re- 

 sults obtained and to assess the aging 

 techniques presently used. In accor- 

 dance with the sexual dimorphism of 

 this species, the length-weight rela- 

 tionship showed negative allometry in 

 females and isometry in males. The 

 high correlation between increment 

 counts and known age in 75 reared lar- 

 vae from to 38 days old (number of 

 increments = 0. 3894-1-0. 9846-days of 

 age; r=0.98> indicated that the daily 

 deposition of growth increments in sag- 

 ittal otoliths and regular incremental 

 formation begins on day one. This cor- 

 relation validated the use of otoliths in 

 the aging of 176 juvenile specimens 

 between 16.5 and 58.5 cm FL, in which 

 the minimum and maximum ages ob- 

 served were 47 and 176 days, respec- 

 tively. Nevertheless, the progressive 

 increase in complexity with the onto- 

 genic development of these structures 

 suggests that this method may under- 

 estimate age in adult fish, probably 

 owing to the loss of marginal zones of 

 the otolith during the polishing process. 

 Thus, from 150 specimens between 65 

 and 124 cm FL, the interpretation of 

 annuli from scales gave ages up to 3 

 years old, whereas readings of otoliths 

 in 36 specimens of the same size inter- 

 val gave ages between and 1 year old. 

 Growth parameters were calculated 

 from the age-length relationships of 

 otolith and scale readings in juvenile 

 and adult fish, respectively, and from 

 the analysis of monthly length-fre- 

 quency distributions, obtained in 1990 

 and 1991 during the exploitation of ju- 

 veniles from 18 to 70 cm FL (n =4084 1. 

 The values obtained for L„ ranged from 

 72.4 cm FL in unsexed juveniles and 

 1 10.0 cm FL in females both juvenile and 

 adult, whereas k ranged from 1.6/year in 

 juvenile and adult females and 2.5/year 

 in unsexed juveniles. Although the re- 

 sults obtained were quite different ow- 

 ing to the different length and age 

 range considered, similar results were 

 obtained by comparing the growth per- 

 formance index (F), and showed the 

 rapid growth of the species. 



Otolith microstructure, age, and growth 

 patterns of dolphin, Coryphaena hippurus, 

 in the western Mediterranean 



Enric Massuti 



I.E O , Centre Oceanografic de les Balears 



Moll de Ponent s/n, Apdo 291 



07080 Palma de Mallorca 



Spam 



E-mail address emassuti g'dgpesca caibes 



Beatriz Morales-Nin 



Joan Moranta 



C-SI C./U I B  Institut Mediterrani d'Estudis Avancats 



Campus Universitan 



07071 Palma de Mallorca, Spam 



Manuscript accepted 14 April 1999. 

 Fish Bull. 97:891-899 (1999). 



Dolphin (Coryphaena hippurus Lin- 

 naeus, 1758) (Pisces: Coryphaenidae) 

 is an epipelagic, top-level predator 

 species widely distributed in the 

 tropical regions of every ocean 

 (Palko et al., 1982). It migrates 

 widely, and in warmer months in- 

 creases its range to subtropical ar- 

 eas. Thus, it occurs seasonally in the 

 Mediterranean from spring to au- 

 tumn, when surface waters reach 

 temperatures above 16-18°C (Mas- 

 suti and Morales-Nin, 1995); mature 

 specimens are occasionally caught in 

 the swordfish (Xiphias gladius) 

 fishery with surface longlines at 

 this time, and immature juvenile 

 fish are exploited by small-scale 

 fisheries that deploy surrounding 

 purse nets around fish aggregation 

 devices. 



Dolphin age and growth have 

 been determined by means of scale 

 annuli (Beardsley, 1967; Rose and 

 Hassler, 1968), daily growth incre- 

 ments in otoliths (Oxenford and 

 Hunte, 1983; Uchiyama et al., 

 1986), and modal progression analy- 

 sis (Wang, 1979; Murray, 1985). In 

 addition, some growth studies have 

 been made of fish of known age 

 reared in captivity (e.g. Hassler and 

 Hogarth, 1977; Ostrowski et al., 



1989; Benetti et al., 1995b). In the 

 Mediterranean, available growth 

 data on this species are related to 

 morphometric relationships (Lozano- 

 Cabo, 1961; Bannister, 1976) and 

 rearing experiments ( Rehones et al., 

 1992;Ayarietal., 1995). 



The objective of this paper was to 

 determine, for the first time in the 

 Mediterranean, the age and growth 

 patterns (including juvenile and 

 adult phases) of C. hippurus. To 

 support age and gi'owth parameters 

 estimated from readings of scales 

 and otoliths, direct validation by 

 means of rearing experiments and 

 indirect validation based on length- 

 frequency analysis were also ap- 

 plied. Otolith microstructure was 

 analyzed to determine increment 

 patterns and morphological changes 

 during growth and to obtain more 

 precise increment counts. 



Material and methods 



From May to November 1990 and 

 1991, fork lengths (FL) of adult 

 specimens (/; = 150) were measured 

 from longline catches. Sex was de- 

 termined on the basis of the sexual 

 dimorphism of the species (Palko et 



