Echinoderm Aquaculture

Nicholas Brown, Steve Eddy

• Publisher: Wiley-Blackwell
• Year: 2015
• Print ISBN: 9780470960387
• eBook ISBN: 9781119005971
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Fisheries & Aquaculture
• Index: Technology & Engineering

Sea urchins and sea cucumbers are highly sought after delicacies growing in popularity globally. The demand for these species is rapidly outpacing natural stocks, and researchers and seafood industry personnel are now looking towards aquaculture as a means of providing a sustainable supply of these organism. Echinoderm Aquaculture is a practical reference on the basic biology and current culture practices for a wide range of geographically diverse echinoderm species.

Echinoderm Aquaculture begins by examining the basic ecology and biology of sea urchins and sea cucumbers as well as the breadth of uses of these organisms as a source of food and bioactive compound. Subsequent chapters delineate the specific species of interest invarious geographic regions from around the world. Together, chapters provide a comprehensive coverage of culture practices.

Echinoderm Aquaculture is a practical reference for researchers and industry personnel, and will serve as an invaluable resource to this rapidly growing segment of the aquaculture industry.

Part I
Biology and Exploitation of Echinoderms

Chapter 1
Sea Urchin Ecology and Biology

Larry G. Harris and Stephen D. Eddy

Introduction

Sea urchins are widely distributed in polar, temperate, and tropical oceans, where they are conspicuous members of most benthic marine communities. They play an important ecological role as herbivorous grazers, and their ability to alter algal community states has made them the subject of numerous ecological studies (e.g., Elner and Vadas 1990; Tegner and Dayton 2000; Witman and Dayton 2001; Uthicke et al. 2009). Sea urchins are also used as a model organism in developmental studies and in schools to demonstrate cell division and early development; the purple urchin, Strongylocentrotus purpuratus, was one of the first animal species to have its entire genome sequenced (Sea Urchin Genome Sequencing Consortium 2006). There are about 850 living species of sea urchins, and at least 17 of these are commercially valued as food (Table 1.1), leading to significant sea urchin fisheries in many regions (Andrew et al. 2002; Lawrence and Guzman 2004). Because sea urchins often form dense aggregations when their populations increase, they are very vulnerable to overharvesting. Wild stocks in most regions where they are fished are greatly diminished and aquaculture has been proposed as a means to supply the continued market demand, most of which comes from Japan. The first section of this chapter discusses some of the ecological factors that affect sea urchin abundance, distribution, and vulnerability to overfishing. The second section discusses biological and physiological considerations that may be of interest to sea urchin aquaculturists, such as feeding, growth, reproductive control, and physiological adaptations relevant to intensive culture.

Table 1.1 Commercially valuable sea urchin species

Scientific name	Common name	Country/Region
Anthocidaris crassispina	Japanese purple sea urchin	China, Japan, Korea
Echinus esculentus	European edible urchin	North Sea, NE Atlantic, Scotland
Evechinus chloroticus	Kina	New Zealand
Glyptocidaris crenularis	none	China, Japan, Korea
Heliocidaris erythrogramma	Purple sea urchin	Australia
Hemicentrotus pulcherrimus	Green sea urchin	China, Japan, Korea
Loxechinus albus	Chilean sea urchin	Chile
Lytechinus variegatus	Variegated or green sea urchin	Tropical western Atlantic
Paracentrotus lividus	Purple sea urchin	Mediterranean, Eastern Atlantic
Psammechinus miliaris	Shore or green sea urchin	North sea, Eastern Atlantic
Pseudocentrotus depressus	Purple sea urchin	Japan
Strongylocentrotus droebachiensis	Green sea urchin	North Atlantic & Pacific
Strongylocentrotus franciscanus	Red sea urchin	California, British Columbia
Strongylocentrotus intermedius	Japanese sea urchin	Japan, China
Strongylocentrotus nudus	Dalian purple urchin	Japan, China
Strongylocentrotus purpuratus	Purple sea urchin	North & Central America Pacific Coast
Tripneustes gratilla	Collector urchin; sea egg	Tropical pacific, Australia, Hawaii

Natural History and Ecology

Most sea urchins are broadcast spawners, releasing eggs and sperm into the water column where fertilization takes place, followed by development into a pelagic pluteus larval stage. Environmental cues such as day length and temperature initiate gametogenesis, and spawning is triggered by environmental cues and pheromones to coordinate gamete release. Specific factors that initiate spawning of sea urchins in the field are relatively unknown, although phytoplankton blooms are considered to be an important trigger (Palmer 1937; Kanatani 1974; Cochran and Engelman 1975, 1976; Starr et al. 1990, 1992; Takahashi et al. 1990, 1991).

Gametogenesis and spawning have been well documented for the commercially valuable and widely distributed green sea urchin, Strongylocentrotus droebachiensis. In the Gulf of Maine, North America, the onset of gametogenesis is triggered in this species by the shorter day lengths following the autumnal equinox in September (Walker et al. 2007). Natural spawning of S. droebachiensis usually occurs over an extended period in the spring months (March to June) and there may actually be more than one spawning event for a population (Keats et al. 1987; Meidel and Scheibling 1998). During each spawning event, males spawn first by releasing spermatozoa, which begin swimming upon contact with seawater. Ova are then released into a cloud of actively swimming spermatozoa. In S. droebachiensis, both sexes spawn in response to a small-molecular-weight protein associated with phytoplankton blooms (Himmelman 1975; Starr et al. 1992). Studies by Levitan (1991), Levitan et al. (1992), and Wahle and Peckham (1999) have suggested that fertilization success requires close proximity of spawning urchins. If this is the case, then fishing removal could reduce the population density to a level that adversely affects reproduction. However, other studies suggest that factors other than proximity determine reproductive success (Meidel and Yund 2001; Yund and Meidel 2003). Normally, sea urchins tend to be cryptic in distribution and seldom aggregate in the open, which calls into question whether reproductive success requires high population densities (aggregations). The author has observed large numbers of the sea urchin Echinothrix sp. releasing eggs or sperm at sunset on the Kona Coast of Hawaii; individuals were dispersed over many hundreds of meters rather than in aggregations, but the timing was coordinated.

The reproductive success of broadcast spawning invertebrates has been likened to a “recruitment sweepstakes” (Flowers et al. 2002). Variability in ocean conditions and high mortality rates of larvae and newly settled juveniles mean that random events can affect the reproductive success of spawning adults during each season. This makes it difficult to predict recruitment from year to year, and variable reproductive success might also influence the genetic structure and diversity of year classes (Flowers et al. 2002). As urchin larvae drift in the water column for 1 month or longer before settling and are not strong swimmers, the urchins that recruit to an area of bottom likely drifted in from somewhere else. Mortality due to micropredators during the initial settlement phase can be very high and recruitment appears to be more a case of differential survival rather than selective settlement (Harris et al. 1994; Harris and Chester 1996). In the 1980s in the southern Gulf of Maine, densities of newly settled S. droebachiensis on the bottom could be measured in thousands per meter square (Harris and Chester 1996), with numerous pinhead-size (<1.0 mm) urchins found on urchin barrens (Harris, personal observations); but within a couple of weeks, only scattered patches of juvenile urchins could be observed and most of the small urchins had disappeared. Breen and Mann (1976) reported that recruitment of S. droebachiensis was higher in urchin barren communities and seldom occurred in kelp bed communities. However, Harris et al. (1994) found that settlement did occur within algal-dominated environments, but survival was highest in barren communities. There is also variation in settlement by depth with higher numbers in shallower habitats (Martin et al. 1988; Harris and Chester 1996).

One of the most signific...

Table of contents

• Cover
• Title Page
• Copyright
• Table of Contents
• List of Contributors
• Part I: Biology and Exploitation of Echinoderms
• Part II: Sea Urchin Aquaculture
• Part III: Sea Cucumber Aquaculture
• Index
• End User License Agreement