Variability of monthly catches of 

 anciiovy Engraulis encrasicolus 

 in tiie Aegean Sea 



Konstantinos I. Stergiou 



National Centre for Marine Research 



Agios Kosmas, Hellinlkon, Athens 16604, Hellas 



In a recent paper, Stergiou (1990a) 

 showed that the autoregressive 

 terms of an ARIMA model describ- 

 ing the monthly fishery of the an- 

 chovy Engraulis encrasicolus in 

 Hellenic waters indicated a 2- to 

 3-year periodicity in catches. A 

 similar cycle has also been shown 

 for anchovy in the Azov (Demen- 

 t'eva 1987) and Adriatic Seas (S. 

 Regner 1985). In comparison, long- 

 term periodicities have been shown 

 for Engraulis mordax off California 

 (Soutar and Isaacs 1974). In this 

 present study, I examined the vari- 

 ability of the Hellenic monthly 

 catches of anchovy during the 

 period 1964-87 using spectral 

 analysis. 



The purse-seine fishery landed 

 51,282 t of fish which comprised 

 49% of the total Hellenic catch in 

 1987 (Stergiou 1990b). Anchovy 

 comprised 46.6% of the 1987 purse- 

 seine catch; the remainder included 

 sardine Sardina pilchardus, horse 

 mackerel Trachurus sp., bogue 

 Boops boops, chub mackerel Scom- 

 ber japonicus, and bonito Sarda 

 sarda (Stergiou 1990b). Ninety per- 

 cent of the mean annual anchovy 

 catch (1964-85) was caught in the 

 northern, northwestern, and west- 

 ern Aegean Sea (Stergiou unpubl. 

 data; no data are available for 

 monthly catches per major fishing 

 area). A recent study of genetic 

 distances, based on electrophoretic 



o 

 o 

 o 



3 - 



B 2 



Jan 1964 Jan 1969 Jan 1974 Jan 1979 



Month 



Jan 1984 Dec 1987 



Figure 1 



Monthly commercial catches (in 1000 tons) of anchovy Engraulis encra- 

 sicolus in Hellenic waters, 1964-87. 



variation, and of morphometric and 

 meristic characters using multivari- 

 ate analysis does not indicate sep- 

 arate stocks of anchovy (or sardine) 

 in the Aegean Sea (Spanakis et al. 

 1989). 



Monthly catches of anchovy (1964- 

 87, 288 data points) and annual fish- 

 ing effort (in horsepower, HP) of 

 pelagic seiners were gathered from 

 the Bulletins of the Hellenic Na- 

 tional Statistical Service (1968-89). 

 The monthly series was log-trans- 

 formed and detrended to become 

 stationary. The seasonal component 

 was removed by differencing with 

 lag=12 (Chatfield 1984). To avoid 

 a discontinuity at the end of the 

 data, the resulting series was tap- 

 ered by 20%. The Fast Fourier 

 Transform was used to compute 

 power spectral estimates, and 

 smoothed (5 moving averages) 

 squared amplitudes of the sinusoids 

 were plotted. 



Anchovy catches show a marked 

 seasonal pattern (Fig. 1) and an 

 increasing trend for the years fol- 

 lowing 1980. The increased trend 

 in catch in recent years has raised 

 concern about whether these high 

 catches are sustainable. Due to 

 higher prices of anchovy since the 

 late 1970s, purse-seine fishing in 

 Hellenic waters is anchovy -oriented 

 rather than sardine-oriented (Ster- 

 giou 1986a, 1990a, b). Monthly fish- 

 ing effort by pelagic seiners is not 

 available. However, annual fishing 

 effort of pelagic seiners increased 

 considerably between 1964 and 

 1987 (from 363 boats, 20,316 HP, 

 and 6152 tonnage of boats, to 502 

 boats, 112,310 HP, and 18,922 ton- 

 nage of boats; Hellenic Natl. Stat. 

 Serv., 1968-89). Annual catches of 

 anchovy are highly positively cor- 

 related with annual horsepower of 

 the pelagic seiners [Ln(annual 

 catch) = 8.25 -H0.000013HP; n 24, r 

 -1-0.89, p<0.001)(Fig. 2), indicating 

 that the highly significant linear 



Manuscript accepted 26 July 1991. 

 Fishery Bulletin, U.S. 90:211-215 (1992). 



21 I 



