K P Said Koya

Relating abundance of purpleback flying squid Sthenoteuthis oualaniensis (Cephalopoda: Ommastrephidae) to environmental parameters using GIS and GAM in south-eastern Arabian Sea

The distribution pattern of purpleback flying squid and the relationship between its abundance and environmental variables in the south-eastern Arabian Sea were analysed using a geographical information system (GIS) and a generalised additive model (GAM). Highest abundances were observed during December and January within 10 and 13°N and 71 and 72°E around the Lakshadweep Islands. The mean abundance in the area was 4.21 tonnes/km2 and the maximum sustainable yield (MSY) was estimated as 0.63 million tonnes. GAM indicated that very high squid abundance was associated with low values of dissolved oxygen (6.01–6.27 mg/L), sea surface temperature (28.03–28.62°C), pH (7.75–8.56), salinity (30.42–34.48 psu), chlorophyll-a (0.4–0.6 mg/m3), zooplankton biomass (0.23–0.64 mL/m3), and shallow 20°C isotherm (101.2–134.7 m) and mixed layer depth (17.8–29.8 m). As a carnivore from paralarval stages, S. oualaniensis depends on secondary and tertiary production to sustain its population for which primary production is used up. In the tropical Arabian Sea where temperature differences are not so pronounced, S. oualaniensis distribution was found to be related to a low but very narrow sea surface temperature (SST) band. There is sufficient fishable biomass in the area to possibly launch a new targeted oceanic squid fishery from the western seaboard of India.

A new record of Titan cardinalfish, Holapogon maximus (Apogonidae) along the south-west coast of India

Apogonidae (cardinalfish), a speciose marine family, has about 23 genera and 347 valid species. Mostly shallow water inhabitants of pan tropical/subtropical marine environments, a few are found in brackish and freshwater environments (Nelson, 2006; Fraser & Allen, 2010; Froese & Pauly, 2010). Apogonid fish are usually smaller in size (,100 mm, total length) but a few species of genus, Apogon, Holapogon, Apogonichthyoides, Cheilodipterus, Glossamia and Pseudamia grow to larger sizes (Fraser, 1973; Froese & Pauly, 2010).