A comparison of the effect of urchin size and diet on gonad yield and quality in the sea urchin Evechinus chloroticus Valenciennes

Abstract

We compared the gonad-enhancing effects of two diets (NIWA and NIFA diets) in two size classes of sea urchins (Evechinus chloroticus): small and large urchins with a test diameter of 75.6 ± 1.2 mm and 93.8 ± 0.5 mm, weighing 174.8 ± 7.9 g and 315 ± 5.6 g, respectively. After eight weeks being fed prepared diets, urchin gonad index (GI) had significantly surpassed that of the initial and final samples of wild urchins. Urchins in the NIWA/small treatment had a larger GI than the NIFA/small and NIFA/large treatments. The NIWA/large treatment had a larger GI than the NIFA/large treatment. The overall percentage increase in GI for the NIWA/small, NIWA/large, NIFA/small and NIFA/large treatments were 183%, 135%, 132% and 85%, respectively. In terms of gonad colour (CIELAB), there were no significant differences in gonad redness (a*) or yellowness (b*) between experimental treatments, but there was a significant difference in gonad lightness (L*) with small urchins fed both diets having lighter-coloured gonads than the large urchins fed both diets. Sensory assessment of gonads revealed that gonads from small urchins fed both diets were rated as being of better colouration and more uniform in colour than gonads from large urchins. Gonads of urchins fed the NIFA diet were rated as being less bitter and of better overall taste than gonads from urchins fed the NIWA diet. This study shows that feeding prepared diets to E. chloroticus can significantly increase gonad yield but that different diets can affect the magnitude of GI increase and the taste of gonads, and that smaller urchins appear more suitable for gonad enhancement.

Barrens of gold: gonad conditioning of an overabundant sea urchin

“…3a). These results are consistent with previous studies on other urchin species around the world, which have shown that manufactured diets are more effective at increasing GI than kelp diets (de JongWestman et al 1995, Shpigel et al 2004, Musgrove 2005, James 2006, Woods et al 2008, Phillips et al 2010, Cyrus et al 2013. Artificial diets resulted in mean GI values above 10%, regardless of site, which is better than other attempts at gonad conditioning of H. erythrogramma (Sanderson et al 1996, Musgrove 2005, Senaratna et al 2005.…”

Fitness benefits of size-dependent diet switching in a marine herbivore

“…Decrease in absolute growth rate as a function of size has been observed in other species of sea urchins (e.g. Barker et al 1998;Ebert 2001;Woods et al 2008), so perhaps the group of large urchins chosen in this study had already reached their asymptotic size. The decrease in size by large H. purpurascens fed D. pulchra may be due to nutrient resorption from several body parts, including their tests, for survival.…”

Seasonal changes in the biochemical composition ofEvechinus chloroticusgonads (Echinodermata: Echinoidea)

“…FAAs in E. chloroticus gonads have been grouped by Woods et al (2008) according to their general flavour-enhancing (desirable) or flavour-detracting (undesirable) characteristics for the sushi palate. Flavour-enhancing FAAs are typically sweet (glycine, alanine, proline, serine and threonine) or umami (glutamate and asparagine) tasting.…”

“…Flavour-enhancing FAAs are typically sweet (glycine, alanine, proline, serine and threonine) or umami (glutamate and asparagine) tasting. Flavour-detracting or undesirable FAAs are bitter-or sour-tasting amino acids such as valine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine and tyrosine (Woods et al 2008). The distinctive seafood flavour of E. chloroticus gonads is caused by the relative concentrations of both desirable and undesirable FAAs.…”

“…Previous studies on E. chloroticus gonads have primarily focused on the gonad yield and sensory properties Goebel & Barker 1998;James 2006;James et al 2007;James & Heath 2008;Woods et al 2008). In the most recent study, Phillips et al (2009) sampled 170 urchins over 23 months and related sensory properties to gender and season.…”