Is HPLC the best way to detect residues from anti-coagulant rodenticides
UV(/VIS) spectroscopy is the most common HPLC detection method, it's quite cheap and powerful but you can only detect substances which absorb light in the range you are using for detection. You also don't get any real structural information, most of the time identification is only possible using reference material. But most HPLC systems will be equipped with such a detector.

Fluorescence detectors can be used for fluorescent molecules and usually you got a much lower limit of detection. Like for UV/VIS you don't get structural information, but identification works quite well, since you can selectively only detect molecules with the used excitation and emission wavelengths.

Other detectors would be for example refractive index detector, which only really work well if HPLC is run isokratic or MS, which gives you structural information.