[spook1456 (OP)]

I know that particles containing strange anti quarks have their strangeness measured in positive but why do  strange paritcles have their strangeness measured in negative for example
Particle symbol        Strangeness
κ‾ (kaon)                ‾1
Ω‾                       ‾3
Λ°                       ‾1
Σ‾                       ‾1
Ξ‾                       ‾2
Ξ°                       ‾2

[JP]

I don't know the details, but I trust wikipedia on this one:

The terms strange and strangeness predate the discovery of the quark, and were adopted after its discovery in order to preserve the continuity of the phrase; strangeness of anti-particles being referred to as +1, and particles as −1 as per the original definition. For all the quark flavor quantum numbers (strangeness, charm, topness and bottomness) the convention is that the flavor charge and the electric charge of a quark have the same sign. With this, any flavor carried by a charged meson has the same sign as its charge.

so particles can have both positive and negative strangeness.