The above official link has many sections. Here is the link for the official language poll ("Enquesta d’usos lingüístics de la població 2008"), which includes mother-initial/identification/habitual language details (official data):

http://www.idescat.cat/cat/idescat/publicacions/cataleg/pdfd...

"Initial language" (page 45):

Catalan: 31.6%, Spanish: 55%.

"Identification language" (page 48):

Catalan: 37.2%, Spanish: 46.5%

"Habitual language" (page 51):

Catalan: 35.6%, Spanish: 45.9%

Edit: in my first comment in this thread I spoke from memory. Also, the data from the 2013 poll (official data):

https://www.idescat.cat/cat/idescat/publicacions/cataleg/pdf...

"Initial language" (page 45):

Catalan: 31%, Spanish: 55.1%.

"Identification language" (page 46):

Catalan: 36.4%, Spanish: 47.5%.

"Habitual language" (page 49):

Catalan: 36.3%, Spanish: 50.7%.

Thank you!

EDIT: Seems like that's the old poll. There's a new one from 2013, in which both Catalan and Spanish grew as the habitual languages. It still doesn't reach 55%, though.