Iglesias, M. (Magdalena)

Morales-Nin, B. (Beatriz)

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Iglesias, Magdalena

Morales-Nin, Beatriz

Digital.CSIC

Fishery and growth of Aphia minuta off Majorca island

Repositorio Institucional Digital del IEO

295 Fishery and Growth of Aphia minuta off Majorca lsland M. IGLESIAS (') and B. MORALES-NIN ( .. ) "' Instituto Espanol de Oceanografia, Centro Oceanografico de Baleares, PALMA DE MALLORCA (Spain) ,.,. Institut d'Estudis Avam;ats Illes Balears, Campus Universitario, PALMA DE MALLORCA (Spain) Aphia minuta or "jonquillo" is a pelagic neritic species, belonging to the family Gobiidae, captured around Majorca Island during the months of December through March by the artisanal fishery fleet. Its importance is based on the fact that it has a great acceptance on the mai:ket together with the R.r~ce it reaches, and because it is one of the few specific fisheries of the winter season for the coastal fleet. The "jonquillo" is captured with a fishing-net ("jonquillero") which combines purs~seine and trawling. This species meets during the winter months forming shoals for reproductive purposes. Its pelagical habits during this period allow finding them easily using the echo sounder. They are basically found inside the bays (Palma, Pollensa and Alcudia), at bottoms between 20 and 70 meters of depth, above sand and seaweed areas (Posidonia oceanica). In figure 1 the importance of captures of "jonquillo" from Majorca Island in the last ten years can be observed, with amounts that lay between 20 and 80 metric tons. The length-frequency distribution from December 1990 to March 1991 is shown in figure 2. The range of sizes oscillates between 14 and 45 mm. The average size by month is doubled from the beginning to the end of the season. Batacharya 's Modal Progression Analysis (1967) was applied to these data, in order to identificate different cohorts. In table 1 we may observe a monthly series of length modes which go on evolving in time. The mean average increases by month. To interpret these data and being Aphia minuta a species of one year of life span, we determinated the age of t he individuals by using the daily growth rings on otoliths sagit-ta {METHOT and KRAMER, 1979). The otoliths (N = 20) belonged to fishes between 17 and 44 mm of total length corresponding to ages from 64 to 217 days. The good accordance on sizes and age strongly suggested the adecuation of the daily rings for ageing the species. However, further validation is necessary. .. .,~~~~~~~~~~~~ ... N M 11 • 17 .-....... Fiqure l. - Captures from 1982-91. The growth parameters (VON BERTALANFFY, 1938) were calculated by a stadistical programme which uses the Marquant's algorithm {"Fishpann") by the iterative calculation of parameters, and by the method based on the length-frecuency analysis ("Elefan", PAUL Y and DAVID, 1981). The growth parameters determined are : 1) Otoliths ' L.. = 42.62 mm; K = 6.35 2) ELEFAN' L..= 45.62 mm; K = 6.352; lo= 0.1123. XII I II III IV 17 19 25 27 Table 1. - Modal clases by month. 25 26 30 35 35 39 30 33 34 38 39 39 I~ 11 • •• ': . . . . . .. · . ...\ • . 1 . .. . \ ·= . . .·. ). . . ·.. .· .. .. . :. . .... _ -1110 ... nt - ...... .,, ......... - ...... .. ---"1 Figure 2. - Length distribution of 11 jonquillo11 off Majorca. REFERENCES BERTALANFFY L. VON, 1938.- A quantitative theory of organic growth. Hum.Biol. 10:181-213. BHATTACHARYA C.G., 1967.- A simple method of resolution of a distribution into Gaussian component. Biometrics 23:115-135. METHOT R.E. &:: KRAMER D., 1979.- Growth of northern Anchovy Engraulis encrasicholus larvae in the sea. Fish.Bull. 77:413-423. PAULY D. & DAVID N., 1981.- ELEFAN 1, a BASIC program for the objective extraction of growth parameters from length-frecuency data. Meeresforsh 28:205-211. Rapp. Comm int. Mer Médit., 33, ( 1992). 1 

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Fishery and growth of Aphia minuta off Majorca island

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