Comparison of morphology and edible tissues of two important commercial crayfishes, the noble crayfish, Astacus astacus Linné, and the red swamp crayfish, Procambarus clarkii (Girard) (Decapoda, Astacidae and Cambaridae)

Abstract

Sexually mature Astacus astacus (37–64 mm cephalothorax length) and Procambarus clarkii (35–70 mm cephalothorax length) differed significantly in appearance. Astacus astacus had larger chelae and broader bodies; however, cephalothorax length-body weight regression curves of males and females of the two species did not differ significantly. Yields of edible muscle, chelae and abdomens were greatest, on a percentage basis, for crayfish in the 40–50 mm cephalothorax length range. Male P. clarkii over 50 mm cephalothorax length yielded comparable amounts of edible muscle to like-sized male A. astacus but female P. clarkii did not as chelae were significantly smaller than those of males or both sexes of A. astacus. Muscle composition was comparable in both species, having the following levels of moisture, protein, lipid, and energy: 79–85%, 80–88%, 13–50 mg/g, and 19 000–22 000 joules/g, respectively. Waste products remaining after removal of abdominal muscles and digestive glands were more protein rich (33 vs. 24%) and had higher energy levels (11 725 vs. 10 950 j/g) in A. astacus than in P. clarkii. This could be accounted for by lower ash (44% vs. 47%) and dry matter (28% vs. 37%) levels in A. astacus.