IMPLEMENTATION OF WAVELETS TO DETECTION OF FISH POPULATION

Öz

The influence of climatic oscillations (based on NAO and ENSO) on monthly catch rates of fish population such as blue fish and sea bass (pomatomus population between 1991-2008) were analyzed in Black Sea and Marmara Sea by wavelet transform (Wavelet 1-D and continuous wavelet 1-D) with DMeyer for 7-Levels. Wavelet analysis is an efficient method of time series analysis to study non-stationary data. Wavelet analyses allowed us to quantify both the pattern of variability in the time series and non-stationary associations between fish population and climatic signals. Phase analyses were carried out to investigate dependency between the two signals. We reported strong relations between fish stock and climate series for the 4- and 5-yr periodic modes, i.e. the periodic band of the El Niño Southern Oscillation signal propagation in the Black and Marmara Seas. These associations were nonstationary, evidenced from 1995 to 2008. Warm episodes matched increases of longline catch rates of bigeye during the 1970–1990 time frames, whereas the strong 1997–1998 warm event matched a decrease of purse seine catch rates of yellowfin. We discussed these results in terms of changes in catchability for purse seine and longline. The results of this study were compared with former harmonic analyses to explain seasonal effects of NAO and ENSO on fish population.

Anahtar Kelimeler

• Time Series, Wavelet Analysis, ENSO, NAO.