The northern subspecies,
Sarda chiliensis lineolata, is a component of the commercial purse seine fishery as well as a popular recreational fish in southern California. Catch landings for this subspecies have greatly fluctuated, and therefore it is difficult to estimate the effect of fishing on its population. It is not clear what is causing these fluctuations. Pacific Bonito populations fluctuate on a decadal scale in a similar manner as the northern anchovy. Current conditions indicate that the eastern Pacific is in a warm water regime that favours Pacific Sardine over Northern Anchovy, which is a primary prey species for Pacific Bonito. It is therefore thought that these fluctuations in both anchovy and Pacific Bonito are associated with warm and cold water periods of the Pacific Decadal Oscillation (California Department of Fish and Game 2010).
Commercial landings for this subspecies have declined steadily since the mid 1980s, but have increased moderately in recent years, from 291 metric tons in 1997 to 803 metric tons in 2008. The trend over the last 15 years seems to be low landings for most years interspersed with high yield years. Competition with higher valued fisheries was likely part of the decline observed in landings during the 1980s and 1990s. Additionally, increased regulation, decreased stocks and lower market demand likely contributed to the decline. In 1982, Mexico began restricting foreign vessel access to its near-shore fisheries. Prior to this closure, 50–90% of Pacific Bonito landed in the United States was caught off the coast of Baja California, Mexico. Now less than 10% originates in Mexican waters (California Department of Fish and Game 2010).
FAO reported landings for Sarda chiliensis (both subspecies) highly fluctuate and range from 35,016 tonnes reported in 1950 to 11,3161 tonnes in 1961; to 2,383 tonnes reported in 2003 and 6,243 tonnes reported in 2006 (FAO 2009). Landings in California and Mexico have fluctuated greatly over the past 50 years from less than 1,000 metric tons to nearly 14,000 mt in the early 1970s (worth $1,222,000 in total California landings in 1976) (Collette and Nauen 1983). Combined landings of U.S. and Mexico in 1995 was about 6,800 mt, while in the last five years (2000–2005), the landings have been under 500 mt (FAO 2009), representing a decline of over 90%, assuming landings are a good proxy for population trends.
The combined Chilean and Peruvian landings of the southern subspecies, Sarda chiliensis chiliensis, went from almost zero in 1,940 mt to a peak of around 110,000 mt in 1961 and dropped off to about 40,000 mt in 1973 (Collette and Nauen, 1983). From 1995–2005 the catch reduction went from around 30,000 mt per year to around 1,000 to 5,000 mt per year (FAO 2009). Reported landings for this species (in Ecuador, Chile and Peru) plunged to between 1,000 and 5,000 mt per year between 1998 and 2005. A conservative estimate is a reduction in catch of around 80% since 1995.
In Peru, however, there was a decrease in effort during the late 1990s which may reflect the decrease in catch at this time. Also drops in catch may be related to reduction in anchovies, but also during this time there was an increase in effort for Jack Mackerel and Scomber japonicus. Although the catch is rising again in 2005 and 2006, this is likely due to an increase in fishing effort.
In Chile, less than 10,000 mt in the 1960 and 1970s was estimated to be caught, and this was the period of the highest catches (R. Sierra pers. comm. 2008). FAO data for catches from Chile are not necessarily correct for this species, especially in the 1980s.
In the Eastern Pacific, landings data are combined for two bonito species, S. orientalis and both subspecies of S. chiliensis (IATTC 2008). The maximum catch was 14,000 metric tonnes in 1977 and 1990. After 1999 the total catch dropped from thousands metric tonnes to under 1,000 metric tonnes per year with a minimum of 43 in 2003, but may be increasing again as 3,600 tonnes was reported in 2006 (IATTC 2008). It is most likely that the majority of these landings data are for S. chiliensis chiliensis, as the majority of the catch was from Chile and Peru.
