A depth-dependent assessment of annual variability in gonad index, reproductive cycle (gametogenesis) and roe quality of the green sea urchin (Strongylocentrotus droebachiensis) in Breidafjördur, west Iceland

This pilot study aimed to assess whether depth had an impact on the sexual development and quality of green sea urchin (Strongylocentrotus droebachiensis) gonads, and whether market quality urchins could be found at greater depths than usually fished in Breiðafjörður, west Iceland. Green sea urchins were collected monthly at 32 and 60 m depth sites from September 2016 to August 2017. Development and spawning time at both sites were determined by examining monthly changes in gonad index (GI), gametogenesis (nutritive vs. gamete cell development) and sexual stage progression. Gamete development and sexual staging suggested that depth may not significantly impact sexual development, gametogenesis, or the onset of spawning at the study sites. While minor differences in gametogenesis between sexes were observed at both sites, statistical differences were only found in May at 60 m depth. Sex ratios were nearly 1:1 overall at both depth sites, with no observed incidences of hermaphroditism. Market quality urchins, in terms of GI and color, were found at both sites, though results suggested that increasing depth may have a negative impact on quality. Gonad colors met or exceeded minimum market standards from August to March at both depths, with low incidence of unacceptable coloration, though results suggested that increasing depth had a negative impact on color. Additional research regarding these factors is vital for sustainable utilization.