Abstract.— Reproduction, age, 

 growth, and mortality of the white- 

 mouth croaker Micropogonias fur- 

 nieri in Trinidad, West Indies, were 

 studied. Maturity was attained at 2 

 years of age for both sexes. Spawn- 

 ing occurred year-round with a peak 

 from February to August. The con- 

 dition factor varied with the repro- 

 ductive cycle. The sex ratio was 1:1.3 

 malerfemale. Fecundity ranged from 

 ITxlO-' to 37x10= eggs for fish 

 measuring 27.6-57.2 cm total length. 

 Relationships between fecundity (F) 

 and total length (TL) in centimeters, 

 and body weight (W) and ovary 

 weight (Wg) in grams, respectively, 

 were: F= 2x 10--»TL-^''«; F=0.81 

 Wi«8, and F = 22525 Wg - 81355. 

 The length-weight relationship was 

 W = 0.037 TL-'^. Age was determined 

 using otoliths and the analysis of 

 length-frequency distributions. The 

 von Bertalanffy growth equations 

 were L, = 65.3"il - exp [-0.16(f-F 

 1.6)]} for males and L, = 82.9{1- 

 exp [-0.13(^-1-1.3)]} for females. 

 Total mortality rate was 1.2/year. 

 natural mortality rate 0.4/year, and 

 fishing mortality 0.8/year. Yield-per- 

 recruit analysis showed the white- 

 mouth croaker to be fully exploited 

 in Trinidad. 



Reproduction, Age, and Growth 

 of the Whitemouth Croaker 

 Micropogonias furnieri (Desmarest 

 1823) in Trinidad Waters 



Sherry C. Manlckchand-Heileman 



Zoology Department, University of U/est Indies, St Augustine, Trinidad, West Indies 

 Present address: Institute of Marine Affairs, P O Box 3160, 

 Carenage Post Office, Trinidad, West Indies 



Julien S. Kenny 



Zoology Department, University of West Indies 

 St Augustine, Trinidad, West Indies 



Manuscript accepted 20 February 1990. 

 Fishery Bulletin. U,S. 88:523-529. 



The whitemoutli cvoakev Micropogo- 

 nias furnieri (Desmarest 1823) is 

 found in most of the Antilles, and 

 along the southern Caribbean coast 

 and Atlantic coast of South America 

 from Costa Rica to Argentina (Fischer 

 1978). Important fishing grounds ex- 

 tend fi'om Venezuela to Uruguay. This 

 species is one of the most econom- 

 ically important demersal fish in Trin- 

 idad, where it is caught mainly by 

 trawling and bottom longlines. Juve- 

 nile croakers also constitute a signifi- 

 cant portion of the shrimp by catch, 

 most of which is discarded at sea. 



Relevant studies have been con- 

 ducted in Brazil and include general 

 biology (Vazzoler 1962); age and 

 growth (Rodrigues 1968); reproduc- 

 tion, population diversification, and 

 growth (Vazzoler 1970, 1971); feed- 

 ing habits (Tanji 1974); growth and 

 sexual maturation of juveniles (Cas- 

 tello 1982); and reproductive biology 

 (Isaac-Nahum and Vazzoler 1983). 



Presented in this paper are some 

 aspects of the biology, including re- 

 production, growth, mortality, and 

 yield-per-recruit (Y/R) analysis, of the 

 croaker in Trinidad waters. 



Materials and methods 

 Study area 



The island of Trinidad lies between 

 lat. 10°2'N and 10°50'N and long. 



60°54' and 61°56'W on the South 

 American Continental Shelf. Wide ex- 

 panses of flat, muddy, relatively shal- 

 low substrate are found in the coastal 

 areas where trawling for demersal 

 fish and penaeid shrimps is carried 

 out. The climate is tropical with a dry 

 season from January to June and a 

 wet season from July to December. 

 Sampling was done in the northwest- 

 ern waters of Trinidad in depths of 

 30-60 m. 



Methods 



Between October 1977 and Septem- 

 ber 1982, 2314 croakers were ob- 

 tained by trawling. The vessels were 

 of steel hull, 25-29 m in length, and 

 carrying two side trawls. The open- 

 ing of the trawl nets ranged from 

 13.7 to 18 m at the head end while 

 the cod end mesh size was 2.5 cm. 

 The catch was sorted into species and 

 placed in separate baskets, each with 

 a capacity of about 32 kg. Depending 

 on the size of the catch, 2-3 baskets 

 of croaker were taken at random for 

 analysis. Total length (TL) in centi- 

 meters, body weight (W) and gonad 

 weight (Wg) in grams, and sex and 

 gonad maturity stage were recorded. 

 Four maturity stages were recog- 

 nized macroscopically (following Vaz- 

 zoler 1971): immatiu'e, maturing, ma- 

 ture (ripe), and spent. Mature ovaries 

 were weighed to the nearest gi-am 



523 



