A Northern Range Extension for the Thornback, Platyrhinoidis triseriata

Plant, Richard

A brief account of two instances when Thornbacks were caught by fisherman in Tomales Bay. This area had previously been thought to be outside this species' range. The thornback, Platyrhinoidis triseriata , is listed as having a range extending from Thurloe Head, Baja California, Mexico, to San Francisco, California and is considered rare north of Point Conception, California. On 3 May 1988, Antoine Venghiatis caught a thornback while fishing from shore with hook-and-line in Tomales Bay, approximately one nautical mile northwest of Inverness, California. Fishing depth did not exceed 3 m. This specimen is catalogued at the California Academy of Sciences (CAS 63193) and represents a northern extension for the species. On 7 June 1988 a second thornback was taken and released from a gill net operated by Frank Spenger in ca. 6 m of water opposite Heart's Desire Beach, Tomales Bay. Of additional interest was the capture of a total of 20 thornbacks between 22-26 April 1988 by the commercial trawlers Romance and Pacific sun during three separate tows of a pair trawl near Pacifica, California, (just south of San Francisco). The above information indicates that the thornback may not be as rare north of Point Conception as previously thought.

A Northern Range Extension for the Thornback, Platyrhinoidis triseriata

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