Monthly means of female prosome lengths of six calanoid copepod species from Helgoland Roads, North Sea@en

Samples were collected at Helgoland Roads using a Calcofi net (500 µm mesh, 100 cm diameter). When possible, 60 females of the six species Acartia clausi, Centropages hamatus, C. typicus, Paracalanus parvus, Pseudocalanus sp., and Temora longicornis were randomly sorted and their prosome length was measured with an interactive video image digitizing system to the nearest 20 µm (NIH Image 1.55) on a Wild M3/JVC at 40x magnification usually within 6 months after collection. According to Durbin and Durbin (1978) preservation in formalin caused a significant loss in dry weight, carbon and nitrogen in adult females, mostly during the first 24 h; however, it did not significantly affect the C:N ratio or the cephalothorax length of the animals.