Horse mackerel and false scad stock assessment and catch projections, CECAF Divisions 34.1.3 and 34.3.1
C. Maxim

The carangid represent an important part of the pelagic resources in the East-Central Atlantic Ocean Area. Three species dominate the catches: Atlantic horse mackerel (Trachurus trachurus), Cunene horse mackerel (T. trecae) and False scad (Decapterus rhonchus) which comprise more than 28% to the total catch from Div. 34.1.3 and 34.3.1. The Atlantic horse mackerel biomass attained a maximum level in the second half of the 70s decade, about 1.7 mil. tons and decreased sharply, until 1990, to a maximum of about 0.7 mil. tons. For the period 1991 - 1992, both the total and exploitable biomass, presented the same tendence. The recruitment also decreased, especially after 1985 when it attained its highest level in the last 14 years. According to the catch projections for 1994 the Atlantic horse mackerel stock biomass will maintain the same low level as a result of recruitment reduction in the last five years. The Cunene horse mackerel biomass oscilated, in the period 1979-1992, between 520 and 493 ths. tons, with a maximum of 652 ths. tons in 1986 and a minimum of371 ths. tons in 1990. The stock size decreased as a result of high fishing pressure on the parent stock (age 2-9) and low recruitment after 1985, so yield per recruitment constantly exceeded the optimum value in the last 6 years. As aconsequence of good recruitment in 1991 and 1992 the total biomass in 1994 will rise to 621 ths. tons, with an optimum fishing mortality equal to 0.35 in 1993. corresponding to a catch of 145 ths. tons. The False scad assessment shows that the species has, in the last 20 years, had a biomass which varied between 102 and 223 ths. tons and a level of 142 ths. tons in 1992. The lack of experimental hauls in the recruitment assessment makes it difficult to find the real number of year O age group and catch projections. The recruitment in 1992 was determined at a level of 661 mil. specimens. According to this the False scad total biomass will attain 163 ths. tons in 1994 at an optimum fishing mortality equal to 0.34.

Keywords: Horse mackerel, false scad, assessment, catch projection, East-Central Atlantic Ocean.
Contents of this volume Sci. Mar. 59(3-4) : 611-627 Back PDF
 
 
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