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In this paper we prove that the P(q,\ell ) (q odd prime power and \ell >1 odd) commutative semifields constructed by Bierbrauer (Des. Codes Cryptogr. 61:187-196, 2011) are isotopic to some commutative presemifields constructed by Budaghyan and Helleseth (SETA, pp. 403-414, 2008). Also, we show that they are strongly isotopic if and only if q\equiv 1(mod\thinspace 4). Consequently, for each q\equiv - 1(mod\thinspace 4) there exist isotopic commutative presemifields of order q ^2\ell (\ell >1 odd) defining CCZ-inequivalent planar DO polynomials.

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