92 



Abstract— The roudi escolar Pro- 

 methichthys prometheus is common in 

 deep hook-and-line and longline catches 

 of a small-scale fishery along the slope 

 off the Canary Islands. Population 

 structure, reproduction, growth, and 

 mortality of the species were studied 

 from sampling undertaken from August 

 1992 to July 1995. Range of length of 

 fish in the catches was between 36 and 

 80 cm TL, with a main distribution be- 

 tween 56 and 66 cm. The overall ratio 

 ofmales to females was 1:1.74. Females 

 predominated in all sizes. The sex ra- 

 tio varied throughout the period of 

 study; the lowest discrepancy between 

 males and females, however, was dur- 

 ing the reproductive period. A vertical 

 space partitioning among sexes was ob- 

 ser\'ed. with males predominating from 

 600 to 800 m depth, females from 300 

 to 500 m. The reproductive period of the 

 species was from April to September, 

 with a peak in spawning in June-July. 

 The size at first maturity was 47.41 cm. 

 The parameters of the length-weight 

 relationship for all fish were 

 0=0.004521 and 6=2.98932. Age read- 

 ings of otoliths indicated that the ex- 

 ploited population consisted of nine age 

 groups (III-XI years). The von 

 Bertalanffy growth parameters for all 

 individuals were L^=93.61 cm, ^=0.18/ 

 years, and /„ =-1.54 years. The rates of 

 mortality for all fish were Z=0.49/years, 

 M=0.3.5/years, and F=0.14/years. The 

 length at first capture for the whole 

 population was 51.57 cm. 



Biology of a deep benthopelagic fish, 

 roudi escolar Promethichthys prometheus 

 (Gempylidae), off the Canary islands 



Jose M. Lorenzo 



Jose G. Pajuelo 



Departamento de Biologia (Universidad de Las Palmas de Gran Canana) 



Edificio de Ciencias Basicas, Campus Universitano de Tafira 



35017 Las Palmas, Spam 



E-mail address (for J. M, Lorenzo) losemaria lorenzojSbiologia ulpgc es 



Manuscript accepted 23 April 1998. 

 Fish. Bull 97:92-99 (1999). 



The family Gempylidae consists of 

 16 genera and 23 species. Only 

 seven species are found off the Ca- 

 nary Islands, one of which is the 

 roudi escolar Promethichthys pro- 

 metheus (Cuvier, 1832), the only 

 species recognized to date in the 

 genus Promethichthys (Nakamura 

 and Parin, 1993). 



The roudi escolar is a bentho- 

 pelagic marine fish that has a 

 worldwide distribution in tropical 

 and warm temperate waters. This 

 species generally inhabits waters 

 between 100 and 800 m in depth 

 over seamounts and continental 

 and insular slopes. It migrates up- 

 ward at night, probably forming 

 schools (Nakamura, 1981; Parin, 

 1986; Nakamura and Parin, 1993). 



Published information on P. 

 prometheus is very scarce. The ma- 

 jority of studies describe its morpho- 

 logical characteristics, geographical 

 and depth distribution, and ecology 

 (Nakamura, 1981; Parin, 1986; 

 Nishikawa, 1987; Nakamura and 

 Parin, 1993). Only Lorenzo and 

 Pajuelo (1995) have studied some 

 biological aspects of the species. 

 These authors carried out a prelimi- 

 nary study on the sex ratio, repro- 

 duction, and age and growth of 

 roudi escolar off the Canary Islands 

 (central-east Atlantic) on the basis 

 of a small number of specimens dur- 

 ing one life cycle. This paper is an 

 extension of their work, analyzing, 



in addition to all those aspects, 

 population structure and mortality. 

 The roudi escolar is common in 

 the catches of the deep hook-and- 

 line and longline small-scale fish- 

 ery over the slope off the Canary 

 Islands. In this area, this species is 

 captured year round without signifi- 

 cant seasonal differences in landings. 



Materials and methods 



Between August 1992 and July 

 1995, the TL (cm) of 1879 specimens 

 of roudi escolar was measured 

 monthly from commercial catches of 

 the small-scale fleet. Fish were 

 caught with baited hook-and-lines 

 and longlines at depths of 285-870 

 m around the islands of the Canary 

 archipelago (Fig. 1). 



A subsample was taken by a ran- 

 dom stratified method from each 

 sample for biological examination. In 

 total, 776 individuals were analyzed. 

 For each fish, the TW (0.1 g) and the 

 weight of the gonads (0.01 g) were 

 measured, and sex and stage of matu- 

 ration were ascertained macroscopi- 

 cally. The latter was classified as fol- 

 lows: I = immature; II = resting; III = 

 ripe; IV = ripe and running; V = spent. 

 Sagittal otoliths of the fish were ex- 

 tracted, cleaned, and stored dry. The 

 length-frequency distribution of indi- 

 viduals in catches was calculated. 

 Data were pooled for 1992-95. 



