Structural dynamics of Sri Lankan artisanal tuna fisheries: Evidence from a 73 year time series and econometric analysis

This study employed advanced econometric methods to analyse 73 years (1950-2023) of catch data for skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares) tuna from Indian Ocean Tuna Commission (IOTC) database. Bai-Perron tests identified four structural breaks at 1966, 1985, 2005 and 2014 (p<0.01), delineating five developmental phases. Regime switching models revealed differential volatility patterns, with skipjack showing higher volatility. Low volatility regime for skipjack showed mean returns of 0.084 (SD = 0.156, duration 8.7 years) while high volatility regime showed returns of -0.023 (SD = 0.387, duration 4.2 years). Johansen cointegration confirmed long-run equilibrium (trace=23.47, p<0.01) with error correction coefficient -0.31 (half-life 3.2 years). Non-linear ARIMA-GARCH models achieved 42% and 34% MAPE (Mean Absolute Percentage Error) reduction for skipjack and yellowfin respectively versus linear models. These findings demonstrate complex nonlinear catch dynamics, providing robust frameworks for tropical tuna management under changing conditions.