Climate influence on oil sardine and Indian mackerel in Southeastern Arabian sea

The  anomalies  of  sea  surface  temperature,  coastal  upwelling  index,  rainfall,  multivariate  ENSO  index  and  chlorophyll a  were  analysed  and  correlated  with catch  rate  anomalies  of  oil sardine  and  Indian mackerel  exploited  by  purse  seine  along  the  coastal  waters  off  Karnataka, India in South-Eastern Arabian Sea  during  period  1990–2014.  The  purse  seines  in  Karnataka contributed  on  an  average  75%  and  65%  catch of  oil  sardine  and  Indian  mackerel  respectively.  The  catch  rate  anomalies  of  oil  sardine,  showed  a  significant  positive  correlation  with  sea  surface  temperature  and  negative  statistical  correlation  with  multivariate  ENSO  index.  Such significant relationship was not observed in the case of Indian mackerel. The  relationship  of  those  parameters  to  variations  in  catch  distribution  of  oil  sardine  and  Indian  mackerel  was  explored  with  a  generalized  additive  model.  The  GAM  results  indicated  that  for  sardine, sea  surface  temperature  ( R–sq  =  0.339)  with  40.8%  deviance  and  for  mackerel, chlorophyll a (R–sq  =0.419)  with  58.9%  deviance  were  better  than  other  climatological  factors  and  can  be  considered  as  a  climatological  predictor  of  catches  in  the  region.  The study  also  indicated  a  combination  of  sea  surface  temperature  and  multivariate  ENSO  index  anomalies  had  better  deviance  of  56%  for  oil  sardine