Sea Urchin Fishery Research Articles

Hierarchical statistical framework to combine generalized depletion models and biomass dynamic models in the stock assessment of the Chilean sea urchin (Loxechinus albus) fishery

Generalized depletion models are useful for representing catch dynamics when biological compositional data are lacking but high frequency records of catch and effort are available. A shortcoming of these models is that although they estimate vulnerable abundance they do not provide direct information on the productivity of the stocks. Here we combine generalized depletion models with a biomass dynamic model of the Pella–Tomlinson type. The inference framework is hierarchical, with initial biomass estimates from generalized depletion models being used as input to the biomass dynamic model to estimate its hyper-parameters. Two hierarchical inference approaches are employed: the standard state-space framework and a new hybrid marginal-estimated approximation to the likelihood function, which make different simplifying assumptions. We apply this assessment approach to the first Chilean fishery with a Management Plan, the southern sea urchin fishery. Results from both hierarchical inference methods show a stock fluctuating between high and low biomass levels, for which maximum sustainable yield appears as a risk-prone annual harvest policy. Given this we propose an alternative annual harvest rate corresponding to the average latent productivity over the years of peaks and troughs of biomass fluctuations.

Mismatch between biological, exploitation, and governance scales and ineffective management of sea urchin (Paracentrotus lividus) fisheries in Galicia

The spatial structure of fishery resources influences stock dynamics and finally the fishery. Therefore, this aspect should be included as a key topic in the assessment and management of fisheries. The fishery of the sea urchin Paracentrotus lividus in Galicia has been used as case study to demonstrate how the mismatch between biological, fishery and management scales causes failures in the governance, giving rise to over-exploitation. P. lividus is spatially distributed in nested biological units: patches, micro-stocks, local populations and metapopulations. Fishing operations are local exploiting micro-stocks; however management units in Galician comprise usually more than one local population. This pattern allows the depletion of several micro-stocks without any short-term signals in the exploitation rates over the complete managed territory. Management units should be redefined according to the boundaries of the local populations. In addition, the implementation of reserve networks or a rotation system could allow to effectively managing the resource at a fine-scale. Any of both regulations could also compensate the inverse density dependence that regulates recruitment and fecundity in this species.

A framework to assess the vulnerability of California commercial sea urchin fishermen to the impact of MPAs under climate change

This paper describes the development of a Livelihood Vulnerability Index (LVI) that estimates the relative ability of California commercial sea urchin fishermen to cope with the change associated with proposed marine protected areas. A key goal in establishing marine protected areas is to maximize conservation benefits while minimizing the potential negative impacts to local fishing communities. However, current impact analyses largely assume a linear relationship between percent of fishing area or revenue lost with the magnitude of impact to fishermen. The LVI described in this paper aims to provide an additional dimension to impact analyses in which the adaptive capacity of individual fishermen is examined to estimate the differential abilities of fishermen to cope with the loss of fishing areas or revenue. This paper advances vulnerability assessments as it develops a novel framework for identifying and measuring drivers of vulnerability for understudied fishing populations whose livelihoods depend upon marine resources. This vulnerability assessment is intended to inform the design of marine protected areas by enabling researchers to incorporate the adaptive capacity of fishermen into socioeconomic impact analyses. The LVI was developed for the California commercial sea urchin fishery in the context of proposed marine protected area networks develop through the California Marine Life Protected Act planning process. As climate change advances there is an increasing need to identify vulnerable and resilient populations and ways to bolster adaptive capacity given the environmental and economic changes ahead.

Mismatch between biological, exploitation, and governance scales of sea urchin (Paracentrotus lividus) fisheries in Galicia

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Modeling fine scale urchin and kelp dynamics: Implications for management of the Maine sea urchin fishery

The Maine sea urchin fishery is a classic boom–bust fishery in which efforts to sustain the resource failed despite the creation of a co-management system. We report on ethnographic work undertaken to assist in the development of a fine scale model of the natural system of this fishery. The development of the natural system model required understanding the key linkages between the biology and ecology of the sea urchin and the behavior of fishermen. Information was gathered from the primary scientific literature and from interviews with sea urchin industry members and scientists. Urchin–kelp interactions at a very fine scale create patchy, almost sedentary aggregations of urchins. Settlement of larval urchins appears to be ubiquitous; however, after settlement patches of urchins operate as nearly independent demographic units. In the short term – months to several years – the abundance of urchins in any patch and the spatial dynamics within these patches are determined largely by the actions of fishermen. Consequently, the resource can be characterized as a dynamic fitness landscape in which the spatial structure of urchin patches is the principal determinant of fishermen's harvesting strategies and fishermen's activities are the principal determinant of the spatial structure of urchin patches. While doing the interviews for the natural system model, we developed a fine scale alternative to the usual theoretical explanation of overfishing. The scale of management in the fishery occurs at a much broader scale than the demographically relevant scale of urchin patches. This results in a mismatch of ecological and management scales that leave each patch in the fishery in an open access state, resulting in a very fine scale form of serial overfishing that removes, piece-by-piece, discrete, local aggregations of sea urchins.

Social-Ecological Scale Mismatches and the Collapse of the Sea Urchin Fishery in Maine, USA

Scale mismatches result in incomplete or ambiguous feedback that impairs the ability to learn and adapt and, ultimately, to sustain natural resources. Our aim is to examine the sea urchin fishery in Maine, USA to better understand the multiscale, social, and biophysical conditions that are important for the design of institutions that might be able to sustain the resource. During the late 1980s and 1990s, the Maine sea urchin fishery was a classic gold rush fishery. In the beginning, the fishery was characterized by an abundant resource with little to no harvesting activity, followed by a period of rapid increase in landings and effort that led to a subsequent and persistent decline in the sea urchin population and a significant reduction in effort. We conducted semistructured interviews with scientists and experienced fishermen to understand the multiscale, social, and biophysical conditions that influence fishermen’s harvesting strategies, and the implications of this for the design of institutions for successful resource management. The current co-management system includes an advisory body made up of industry members and scientists it also includes limited entry, and additional input control mechanisms. Many of these measures are implemented at a very broad scale; however, we find that the ecological conditions relevant to the sustainable processes occur at the scale of individual fishing sites or ledges, which is a much finer scale than current management. Therefore, the comanagement system maintains an open access system and leaves few incentives for the development of sustainable harvesting strategies among fishermen. The clear suggestion is that the appropriate management system would be one that directly addresses the fine scale ecological and social dynamics within this fishery and gives fishermen property rights over individual ledges (for example, leases). After having briefly reviewed experiences in Canada and Chile, we found that knowledge of the coupled natural and human system at the fine scale is necessary if we are to assess the feasibility of area management in this fishery, because what works in one fishery does not necessarily work in another.

Effects of seasonality on the reproductive cycle of Diadema aff. antillarum in two contrasting habitats: implications for the establishment of a sea urchin fishery

Reproduction of Diadema aff. antillarum was examined between 2002 and 2005 at subtidal rocky bot- toms around the Canary Islands. Two contrasting habitats (urchin barrens and grazing fronts) characterized by dif- ferent levels of food availability were chosen, and factors thought to influence reproductive periodicity were moni- tored, including temperature, photoperiod, phytoplankton abundance and benthic food availability. Histological analyses showed that D. aff. antillarum had an annual reproductive cycle that was relatively synchronous across the studied sites and habitats. Photoperiod was the most significant factor that correlated with gonad periodicity; benthic food availability of 2 month lag was also corre- lated. However, some differences were detected between males and females in the timing of the onset of gameto- genesis. Spawning was synchronized between both sexes from June to August. Results suggest that the optimum time of year to harvest urchin gonads would be between May and June when gonads were maximal in size but not full of gametes. This species may not provide optimal conditions for an industrial scale fishery, as sea urchins occurring in high density had small gonads and those producing larger volume or more marketable gonad tissue occurred in low densities where harvesting costs would exceed profit.

Recruitment patterns and juvenile–adult associations of red sea urchins in three areas of British Columbia

Red sea urchins, Strongylocentrotus franciscanus, form meta-populations which are connected by the dispersal of pelagic larvae. Local adult spawning biomass likely plays only a small role in the local recruitment in terms of larval supply, but larger adult red sea urchins provide protection to conspecific juveniles which are often found sheltered under their spines. Based on survey data collected for the past 15 years in three areas of British Columbia, we used generalized linear models to study the juvenile–adult association, the temporal and spatial variations in recruitment, and the effect of adult population density on recruitment success. The probability for a juvenile red sea urchin to be found under a larger red sea urchin decreased with increasing test diameter (TD) of the juvenile and with decreasing adult density. The probability fell from over 50% for juveniles less than 10 mm TD to almost 0% for juveniles at 40 mm TD. The probability for an adult red sea urchin to provide shelter to conspecific juveniles increased with increasing TD of the adult and with increasing juvenile density, but was generally low (<15%). Recruitment levels varied annually within each area, and differed among three surveyed areas. Adult densities, at least up to certain levels, had a positive impact on the recruitment. Intensive harvesting of red sea urchins in a location likely caused a reduction in the amount of recruitment to the location over the next number of years. Understanding the role of adults in the recruitment process is essential for assessing effectiveness of alternative management strategies for the red sea urchin fishery.

Loss of predators and the collapse of southern California kelp forests (?): Alternatives, explanations and generalizations

It is increasingly argued that human-induced alterations to food webs have resulted in the degradation of coastal ecosystems and even their “collapse.” We examined the evidence for this argument for Macrocystis pyrifera (giant kelp) forests in southern California. Others have concluded that forests in this region collapsed between 1950 and 1970 as a result of sea urchin grazing driven by overfishing of sea urchin predators (sheephead wrasse and spiny lobsters) and competitors (abalone), and that the kelp forests recovered but are currently sustained as a result of a commercial sea urchin fishery that began in the early 1970s. Our examination of the historical record, primary publications, and previously unpublished data showed that there was no widespread decline in the region between 1950 and 1970, but there were localised declines in mainland kelp forests near the rapidly growing cities of Los Angeles and San Diego. The preponderance of evidence indicates that kelp losses were caused primarily by large increases in contaminated sewage discharged into coastal waters, sedimentation from coastal development, and the 1957–1959 El Niño. Increases in active sea urchin foraging were most likely a secondary effect following dwindling food resources. The forests recovered when sewage treatment improved and sewage outfalls were relocated. The effects of fisheries were explored by correlation analysis between kelp canopy cover and commercial sea urchin landings, and among fisheries landings for sea urchins, abalone, sheephead and lobster. These correlations were generally insignificant, but were often confounded by differences in the spatial scale over which the data were collected as well as factors other than simple abundance that affect the fisheries. However, where area-specific data were available, the landings of sea urchins generally tracked kelp abundance, most likely because roe (gonad) development is directly related to food availability. A literature review showed that although sheephead and lobsters may control sea urchin abundance at small spatial scales within some sites, there is little evidence they do so over large areas. That abalone and sea urchins compete, such that sea urchins increased as a result of abalone harvesting, is largely conjecture based on their similar habitat and food utilization. This study shows that kelp forests in southern California did not collapse, and that declines in some coastal sites were caused primarily by degradation of water quality, increased sedimentation and contamination, and unfavorable oceanographic conditions. We conclude that management by species' protection or reserves will not be effective if poor habitat quality impacts the ability of giant kelp to survive and thrive.

A geostatistical approach for the stock assessment of the edible sea urchin, Paracentrotus lividus, in four coastal zones of Southern and West Sardinia (SW Italy, Mediterranean Sea)

Quantitative surveys of the edible sea urchin, Paracentrotus lividus, were conducted in four fishing zones of Sardinia (Southern Italy, Mediterranean Sea), in Autumn 2007. A total of 120 stations were geo-located along a bathymetric gradient ranging from 0 to 10 m. A geostatistical method was used to evaluate spatial patterns in density and to estimate harvestable stocks. Variographic analyses showed that the isotropic Gaussian and spherical models successfully explained the spatial structure of sea urchin assemblages in these areas. Density maps obtained by punctual kriging showed that sea urchin populations tend to be patchy rather than uniform in their density distribution. A combination of mapping and size categories was used to generate diverse scenarios of harvestable stocks (specimens ≥50 mm in diameter) before the start of the current fishing season. We conclude that the geostatistical approach, which takes into consideration the spatial autocorrelation structure of the populations in small areas, seems to be a good estimator of P. lividus density and biomass and for the assessment of its harvestable stocks, and thus provides an initial step towards a scientific approach to the management of local sea urchin fisheries.

Developing a Bayesian framework for stock assessment and decision analysis of the red sea urchin fishery in Baja California, Mexico

The red sea urchin (Strongylocentrotus franciscanus) fishery is of importance to the economy of Baja California (Mexico). The commercial fishery started in the early 1970s as a result of expanding export markets, but has experienced substantial decline in landings and abundance since 1986. Fishery-independent surveys have not been conducted for all fishing areas, thus CPUE and catch data were used to conduct a stock assessment and decision analysis for the red sea urchin stock. The red sea urchin population dynamics was described with the Schaefer biomass dynamic model. Bayesian approaches were used for the estimation of the model parameters and for projecting the population dynamics of the species under different management scenarios, including constant harvest rate and constant catch strategies. This study suggests that the current stock is only 17% of the virgin stock biomass and that, for a constant catch policy, a 10% increase in the current catch rate could potentially cause the collapse of the fishery in 20 years. Simulation results suggested that a constant harvest rate between 15% and 25% would cause the population to recover and maximize the catch in 2024. Higher harvest rate levels would increase the probability of the biomass being less than 40% of the population carrying capacity.

Moving from Data Poor to Data Rich: A Case Study of Community‐Based Data Collection for the San Diego Red Sea Urchin Fishery

AbstractResponding to the need for management of California's nearshore fisheries mandated in state law by the Marine Life Management and Marine Life Protection acts, the San Diego Watermen's Association (SDWA), which includes divers that target local red sea urchins Strongylocentrotus franciscanus, initiated a community‐based data collection program in 2001. In collaboration with independent scientists and biologists from the California Department of Fish and Game, the SDWA developed an ongoing program to gather, organize, and analyze both fishery‐dependent and fishery‐independent data on the local red sea urchin fishery. The goal of the program is to collect data that will support periodical stock assessments needed for sustainable management of existing nearshore fisheries (including red sea urchins) as well as the kelp forest ecosystem on which these fisheries depend. Here, we discuss sampling designs, methods for determining data quality (bias and precision), and methods for detecting change, and we provide some examples of results from the ongoing community‐based data collection program. We also report on (1) the design and implementation of scientifically valid sampling protocols; (2) data quality assurance and control collaboratively conducted with scientists and resource agency biologists; (3) calibration studies to determine accuracy and precision and the magnitude of detectable changes in red sea urchin populations; and (4) visualization and dissemination of data and results and incremental changes in protocols that would facilitate the monitoring of associated biological communities. Finally, we discuss keys for success in this cooperative‐based data collection program and its implications for stock assessment and management of the red sea urchin fishery in California.

Population structure of purple sea urchinStrongylocentrotus purpuratusalong the Baja California peninsula

Purple sea urchin Strongylocentrotus purpuratus is fished from British Columbia, Canada to Punta Baja, Mexico. The North American population has been divided into northern and southern fishery stocks at the break of Point Conception, but little is known about its southernmost distribution along the Mexican Pacific coast of the Baja California peninsula. In this study purple sea urchin populations in six sites along the Baja California peninsula were analyzed using mitochondrial deoxyribonucleic acid restriction fragment length polymorphism (mtDNA RFLP). A homogeneous distribution of three common haplotypes among all sites was observed. A significant F ST value, however, indicated genetic structure mainly due to the haplotype array in San Miguel, Isla Todos Santos and Punta Baja sites, which were characterized by having high haplotype diversity and several unique haplotypes. Homogeneous distribution of haplotypes along the peninsula could have been influenced by the unidirectional California Current system, flowing north to south. Unique haplotypes in Punta Baja and the structure found could be the result of local oceanographic features specific to this major upwelling zone. It may be necessary to consider the Punta Baja populations individually when managing the purple sea urchin fishery in Baja California, as they show signs of being a unique stock.

Management Methods for a Sea Urchin Dive Fishery with Individual Fishing Zones

Abstract Management of the Nova Scotia sea urchin fishery includes several unusual features: one license per fishing zone, fishers increase resource yields over natural levels by controlling the sea urchin-macrophyte cycle, fishers scale fishing effort to market demand, fishers map the resource in their zones, a reference point for good resource management based on a conspicuous habitat feature, an audit of zone management success, and low ongoing input from the management agency. The low mobility of sea urchins and the opportunity for the diver-harvesters to observe the resource directly make this fishery a good candidate for management by fishers. Variable sea urchin growth and reproduction on a small spatial scale and the high cost of stock surveys by diving make the fishery less suitable for government regulation. Fishing zones were allocated based on the length of feeding fronts (i.e., the deep edge of the macrophyte beds where sea urchins aggregate and where most harvesting occurs). Fishers and gove...

Exchange Relationships in Inshore Fisheries1

Research on the long‐term, informal exchange strategies of harvesters and dealers working in inshore fisheries has been important to theory surrounding economic exchange. In transaction costs economics, this research provides evidence for economic exchange governed by trust, and in exchange theory, it provides evidence for the emergence of cooperation and trust. In this article I examine the emergence of economic exchange relationships in the new sea urchin fishery. The research is ethnographic in nature, utilizing a variety of data sources including participant observation, in‐depth interviews, and existing quantitative data. I find that, just as experience or improved efficiency can have an impact on the emergence of trust between exchange partners, potential exchange partners can be deemed untrustworthy based on general characteristics unrelated to the particular individual. Once established, these assessments become part of the strategic context of exchange in the fishery.

Enhancing the Recovery of Depleted Tripneustes gratilla Stocks Through Grow-Out Culture and Restocking

Grow-out culture in sea cages and restocking were undertaken to help rebuild the spawning population of Tripneustes gratilla in Bolinao, Philippines. Higher population densities and incidence of recruits in 2004–2006, as well as steady increase in the catch per unit effort of gatherers, indicate that the sea urchin population is recovering. Growth of reseeded, hatchery-produced sea urchins in two sites was high and comparable to those in grow-out cages. However, natural mortalities were very high (91–99%). Good growth, high survivorship, and potential reproductive output of sea urchins in grow-out cages, aside from immediate socio-economic benefits, demonstrate that grow-out culture is a cost effective option for reestablishing effective spawning populations. Higher recruitment success in Lucero, compared to other sites, may be attributed to local favorable biophysical conditions and to maintenance of an effective spawning population due to enforcement of marine sanctuary rules, size regulation, and the presence of broodstock cages. Results suggest that the establishment of a network of marine protected areas in tandem with grow-out culture may be strategic in enhancing the recovery of depleted populations by maintaining larval exchange to sustain the productivity of sea urchin fishery stocks along NW Luzon.

Impacts of prior mis-specification on Bayesian fisheries stock assessment

One of the key features of a Bayesian stock assessment is that the modeller needs to provide knowledge on model parameters. Priors summarise modellers’ understanding of model parameters and are often defined by a probability distribution function. Priors are often mis-specified with arbitrary and unrealistic accuracy and precision in perceiving the state of nature for the parameters as a result of our limited understanding of fisheries ecosystems. Commonly used probability functions such as normal distribution functions tend to be sensitive to prior mis-specification, resulting in large uncertainty and/or errors in Bayesian stock assessment. Fat-tailed functions such as the Cauchy distribution function have been found to be robust to prior mis-specification. Using the Maine sea urchin fishery as an example, we evaluated the impacts of mis-specification in defining the prior distributions on Bayesian stock assessment. The present study suggests that the quantification of priors with a Cauchy distribution tends to be robust to the prior mis-specification. Given our limited understanding of fisheries a function such as the Cauchy distribution function that is robust to prior mis-specification tends to be more desirable. Future studies should explore the use of other fat-tailed distribution functions for quantifying priors in fisheries stock assessment.

Enhanced production of the sea urchin Paracentrotus lividus in integrated open-water cultivation with Atlantic salmon Salmo salar

Survivorship and performance was investigated for two size classes of the sea urchin Paracentrotus lividus grown adjacent to open-water Atlantic salmon (Salmo salar) cultivation on the north-west coast of Scotland. Juvenile P. lividus were maintained for 12 months at 0 m, 50 m and 2.5 km from the mariculture activity. The sea urchins at the 0 m station showed higher survivorship than at the 50 m and 2.5 km stations and had significantly greater test diameter than at the 50 m station. Only urchins at 0 m developed gonads and, although small, these were of acceptable or excellent colouration in terms of their marketability. Adult P. lividus were maintained for 3 months at 0 m and 15 m from the mariculture activity, either with or without additional macroalgae Laminaria spp. Sea urchins at the 0 m station and fed additional macroalgae showed higher gonadal growth than sea urchins at the 15 m station held without additional food. Gonad colouration in the adult urchins, irrespective of the treatment, was acceptable or excellent. The 0 m station also received significantly greater quantities of particulate organic matter (POM) than the other stations in both the juvenile and adult experiments. At the 0 m station, the presence of the fatty acid 22:1n-11 and elevated levels of the long chain n-3 fatty acid DHA 22:6n-3 in the gonadal tissue of the urchins confirmed the consumption of fish farm derived POM and highlighted the potential human health benefits from consuming sea urchin roe.The results show that P. lividus can thrive in the salmon culture environment and suggests that the integration of P. lividus with Atlantic salmon can provide a viable means to culture this species, even at this northerly latitude. Salmon-sea urchin co-culture would enable fish farms to diversify into producing a second highly valuable product and would reduce the increasing worldwide pressure of sea urchin fisheries on wild stocks.

The impact of commercial and recreational harvesting for Paracentrotus lividus on shallow rocky reef sea urchin communities in North-western Sardinia, Italy

The fishery for the edible sea urchin Paracentrotus lividus is of great importance to many European regions, although in some of them this species has shown a wide scale decline in recent years. This paper reports on direct (on P. lividus) and indirect (on the co-occurring but not fished echinoid, Arbacia lixula) effects of sea urchin harvesting in shallow rocky reefs in North-western Sardinia (Italy, central-western Mediterranean Sea), where this activity is intensively practised. Density, size (test diameter), and biomass of both species were assessed in autumn 2004 at two locations impacted by P. lividus fishery, and at two controls within an adjacent Marine Protected Area. Density of P. lividus and A. lixula was significantly greater at the controls than at the exploited locations. The average test diameter of P. lividus was also significantly larger at the controls, where large-sized specimens (i.e. >5 cm) were notably more abundant. The average size of A. lixula did not significantly differ between the impacted locations and the controls. The average biomass of P. lividus was significantly greater at the controls than at the exploited locations, whereas no differences were detected for A. lixula. These results reveal the existence of a heavy fishing impact on P. lividus in North-western Sardinia and the need for regulation of its harvesting to prevent severe direct effects on its populations. Since no indirect effects on A. lixula have been detected, it could be hypothesized that this species did not benefit from P. lividus fishery due to an only moderate competition for habitat and resources between these two echinoids. Implications for management of edible sea urchin fishery are also discussed.

Suspension of annual gametogenesis in North American green sea urchins ( Strongylocentrotus droebachiensis) experiencing invariant photoperiod—Applications for land-based aquaculture

Sea urchin fisheries are valuable commercial resources in the United States with processed gonads sold in Japanese and American markets and maximum US sales of $150M US dollars in 1996. Wild populations of sea urchins on all coasts of the US have been dramatically over-fished. Aquaculture of sea urchins in land-based facilities can help restore commercial populations and preserve this ecologically important herbivore. In this study, we used invariant summer photoperiod to prevent gametogenesis in the North American green sea urchin ( Strongylocentrotus droebachiensis) maintained in a land-based aquaculture system and provided a commercially available formulated feed that promotes maximum growth of intra-gonadal somatic nutrient storage cells called nutritive phagocytes. Results were compared with individuals fed the same formulated feed under ambient photoperiod in cages in the ocean. Monthly samples of gonads from both treatments were evaluated for gonad index, volume fractions of cellular constituents of the germinal epithelium, oocyte diameters and taste. Over the 5 months of this study, gonad indices increased significantly ( p < 0.001) in both treatments from 4.8% ± 0.9 (all values ± SE) initially to 20.5% ± 2.1 under invariant and 23.2% ± 1.4 under ambient photoperiod with no significant difference between treatments ( p = 0.55). Volume fractions of nutritive phagocytes increased to 80.3% ± 5.9 (initial 37.9% ± 7.1) in males and 71.0% ± 6.7 (initial 10.3% ± 4.0) in females ( p < 0.001) only under invariant photoperiod. Nutritive phagocyte lengths increased under both photoperiod treatments, but the volume fraction containing nutrients was higher under invariant photoperiod. Volume fractions of gonial/gametogenic cells increased significantly ( p < 0.001) only under ambient photoperiod from 20.4% ± 5.5 to 37.8% ± 1.8 in males and 0% to 22.6% ± 3.6 in females. The volume fraction of residual oocytes from last year's oogenesis increased under invariant photoperiod while that of both residual and new oocytes increased under ambient photoperiod. Residual oocyte diameters increased from 56.2 μm ± 2.2 initially to 93.5 μm ± 3.7 under invariant and those of residual and new oocytes to 126.0 μm ± 7.3 under ambient photoperiod. Invariant photoperiod yields gonads in both sexes of S. droebachiensis that do not initiate fall gametogenesis but attain large size as their nutritive phagocytes grow substantially in size. A Canadian study of wild-collected S. droebachiensis indicated that gonads taste best when they contain pre-dominantly nutritive phagocytes and not copious gametes, however gonad taste in our study was unsatisfactory suggesting that the only commercially available sea urchin diet requires modification to support commercial development of land-based aquaculture.