Researches on fauna and stock level of the coastal fishes around Oshika peninsula

Representative Organization: Tohoku University

2015/04/01 - 2016/03/31
Once a month

Onagawa Bay (including sea area around Kinkazan Is. and Shizugawa Bay)

Field survey

1. Demersal fishes and benthic animals eel are caught by gill net, pod net, and cage in the Onagawa Bay. Age determination is conducted for the main fisheries resources, for Age-length key. 2. Landings at Onagawa fisheries market are investigated. Age and year class compositions are estimated by the age-length key. 3. Fish compositions are analyzed to evaluate the effect of the Great East Japan Earthquake on fish fauna, and long-term fluctuation in the composition, through investigation on the logbook of set net fisheries around Kinkazan Is. and Shizugawa Bay.

Most two abundant fishes are greenlings and brown hakeling. These fishes dominate the composition in almost all surveys through the period of 2012-2014. The dominancy of them was reduced in autumn season because many migratory pelagic fishes such as gizzard shad were caught every year. In spring, brown sole occupied the composition in 2013 and 2014. CPUE fluctuated in a range of 3-27. There is a tendency that CPUE rise up when the shad and sole occurred seasonally. Year class compositions of black rockfish and brown sole are relatively stable in this survey period. 2010 year class of the black rockfish and 2012 year class are dominant. Other species showed similar changes that the majority 2012 is year classes reproduced before 2011, and the ratio of the year classes before 2011 decreased as year progressed. 2012 and 2013 year classes hatching after 2011 occupied the composition 2014. In the megalobenthos, 27 species (n=1222) were collected. Densities were estimated to be lower than that before the tsunami. In addition, they were almost small sized animals. The benthos received a more direct impact than demersal fishes, but the fauna is recovering gradually.

FY2015 Researches on fauna and stock level of the coastal fishes around Oshika peninsula