I think you are right. They are talking about a lot of female cats hence "le gatte" is correct. If they were a lot of boy cats then it would be "i gatti." However, I think very few people can be sure of what gender a whole load of cats might be so it's unlikey to come up in conversation too often :)
I figured I'd clarify the gender issue with animals such as cats,
as Due seems to be unaware¹ that it could use the (English) gender specific words for cat:
- Il Gatto - The tomcat. (Male cat, singular)
- I gatti - The tomcats. (Male cats, plural)
- La gatta - The molly. (Female cat, singular)
- Le gatte - The mollies. (Female cats, plural)
You also have two other terms for female cats in English:
- Queen - a pregnant or nursing molly.
- Dam - a term reserved exclusively for rare or purebred female felines during the act of recording or maintaining ancestral records for cat breeding.
These are obviously not as commonly used as their equivalents in Italian,
as English is mainly a noun gender-less language, but they still are.
For other animals as well.
(e.g., cavalla - mare, cavallo - colt/stallion - puledro /stallone)
¹ Unaware, or decided that gender-specific words for animals are
not widely enough known, as courses in English might be taken
by many non native English speakers.
You'll never hear someone use the verb 'mangiare' with a direct definitive object such as 'pesce' or 'pasta' etc without the use of an article such as 'la' (pasta) or the preposition 'di'. This sentence may be correct on some technical level I'm not aware of, but an Italian would correct you every time if you said a phrase like this.
It also seems (in reference to fish being plural or not) that it would be "the cats eat THE fish if it were singular. Without the article it sort of implies that there is more than one fish (or that it is fish in general--like I do, or don't, eat meat). I think this is where the "conversational reality" should be considered. Not likely I will be talking about the cat eating fish or fishes!