Sea Urchin Fishery Research Articles

Sea urchin utilisation in Eastern Indonesia

Sea urchins have long been an important component of gleaning invertebrate fisheries and are valued for their highly nutritious gonads. Sea urchin fisheries are often unreported and unregulated, despite increasing indications of overexploitation. Data on the post-harvest utilization of sea urchins are limited, particularly in the Indo-Pacific region. This study at 12 sites across four regions in Indonesia (Sulawesi, Moluccas, Nusa Tenggara, Papua) aimed to provide an overview of sea urchin utilization in eastern Indonesia. Data were collected from July to September 2020 using a questionnaire with a snowballing sampling method. There were 187 respondents (62.6% male and 37.4% female) ranged in age from 3-76 years old, and most had been collecting sea urchins for more than five years. Respondents mostly collected the sea urchins from coral reef or seagrass habitats. Four genera (Tripneustes, Diadema, Echinometra and Echinothrix) were identified. Mean catch ranged from 32 (Makassar) to 169 (Maluku Tengah) individual sea urchin per collection. Most respondents knew local names for sea urchins, especially those they collected. Almost 70% respondents used their catch mainly for home consumption, and only 4.8% respondents mainly selling their catch. Most urchins sold were whole or crudely de-spined, typically fetching IDR 500-1000 each. Additional post-harvest processing before sale included removing the gonads from the test and/or cooking, with a unit price of IDR 5,000-25,000/product. Commonly consumed raw, urchins were sometimes cooked (mostly barbecued). These data indicate a need for efforts towards socio-ecologically appropriate sea urchin conservation and fisheries management to address the widespread indications of increasing exploitation levels and declining sea urchin populations.

Understanding the impact of environmental variability and fisheries on the red sea urchin population in Baja California

IntroductionThe red sea urchin fishery is one of the most important fisheries in Baja California and the only urchin fishery in México; yet little is known on understanding how local, regional, and oceanic environmental variability may affect red sea urchin populations. MethodsWe analyzed how food availability, predator abundance and environmental variability could affect red sea urchin populations developing generalized linear models under different temperature conditions: Pre-heat wave, heat wave, and post–heatwave, including sites where sea surface temperature was above, below, and on average. Models included: a) biological variables: Macrocystis pyrifera (kelp) biomass, red sea urchin (Mesocentrotus franciscanus) density, sheephead (Semicossyphus pulcher), kelp bass (Paralabrax clathratus) and spiny lobster (Panulirus interruptus) catches, and b) oceanographic variables: sea surface temperature, wave power, upwelling index, multivariate El Niño index and North Pacific Gyre Oscillation index. ResultsBetween 65 and 82% of the variability observed in red sea urchin populations was explained by different combinations of variables, depending on the thermal condition analyzed. We observed that local environmental variability, such as food availability and predator harvest are highly important factors in determining red sea urchin population changes, compared to regional and oceanic scale variables such as upwelling, El Niño, or the North Pacific Gyre Oscillation. Results show that the relative importance of these variables changed depending on the spatial and temporal scale being analyzed, meaning that under “normal or average” conditions one set of variables is important, compared to extreme environmental conditions such as El Niño or “the Blob” when a different set of variables explained the observed variability. Urchin predators’ catches were correlated with urchin density during the pre-heatwave scenario, suggesting that under “average temperature” conditions the effect of fishing on predators, and consequently on urchin density is higher than local temperature, the most important variable during warm conditions. DiscussionThis study suggests that in Baja California, red sea urchin harvest has become the most important red sea urchin population control, so efforts should be encouraged and supported by state and federal agencies to promote more resilient ecosystems in the face of environmental uncertainty. Improving management of the commercial species that inhabit kelp forest, could yield benefits for the entire ecosystem, fishers, and the red sea urchin population in Mexico.

Assessing Processing Waste from the Sea Urchin (Centrostephanus rodgersii) Fishery as an Organic Fertilizer

The longspined sea urchin, Centrostephanus rodgersii, is a climate-driven pest species in south-eastern Australia. The harvest of this species is highly encouraged and in Tasmania, the existing fishery is expanding resulting in a large amount of waste that needs disposal. Research into use of waste products as inputs for organic or biodynamic farming systems can help reduce costs of disposal and keep the industry profitable; by sustaining or incrementing sea urchin harvest the industry can assist in their control. In the current study, urchin waste was dried and finely ground to a powder and applied to tomato plants in a greenhouse to examine the effect on growth and productivity. Urchin waste powder (UWP) had a mineral composition of Ca (40 g 100 g−1), Mg (1.7 g 100 g−1), P (0.03 g 100 g−1), Fe (19.34 mg kg−1) and B (38 mg kg−1), a pH 8.06 in water and an Electrical Conductivity (EC) value of 7.64 dSm−1. Seven different treatment rates of UWP (0.3%; 0.5%; 0.8%; 1%; 2%; 3%; 5%), were added to 10 replicate pots containing 4 kg nutrient-poor potting mix planted with tomato (Variety K1) seedlings. Plant growth, yield, quality attributes and mineral content of tomato were measured under UWP treatments with comparison against a Hoagland solution control. UWP influenced tomato growth and productivity proportional to the quantity applied, however, the Hoagland solution control had a significantly greater yield. Potting mix pH increased from 6.8 to 7 and higher available P was detected in potting mix receiving higher rates of UWP. No phytotoxic effects were detected. The highest UWP treatment matched the Hoagland control in fruit quality and nutritional composition. Processing waste from the sea urchin fishery has potential as organic fertiliser or amendment providing plant-available Ca and some microelements such as Boron.

Observations from the Hydrolysis of the Green Sea Urchin (Strongylocentrotus droebachiensis).

There is a large amount of coproduct generated by the sea urchin fisheries around the world as well as a growing interest in removing large quantities of undersize and low value sea urchins from barren areas in the northern Atlantic and Pacific coasts as well as other areas around the world. The authors believe there is scope to develop a hydrolysate product from this and this study gives preliminary observations on the characteristics of hydrolysate from the sea urchin Strongylocentrotus droebachiensis. The biochemical composition for S. droebachiensis is moisture 64.1%, protein 3.4%, oil 0.9%, and ash 29.8%. Amino acid composition, molecular weight distribution, lipid-class, and fatty acid composition are also presented. The authors suggest a sensory-panel mapping be undertaken on future sea urchin hydrolysates. Possible uses for the hydrolysate are unclear at this stage but the combination of amino acids and the relatively high levels of glycine, aspartic acid, and glutamic acid should be further investigated.

Prioritising conservation actions for extremely data-poor species: A risk assessment for one of the world's rarest marine fishes

Effective prioritisation of research and conservation action for threatened species requires understanding the relative importance of the various pressures they face. This can be difficult for rare, cryptic, and data-deficient species, particularly when drivers of population decline are complex and indirectly impact one another. We developed a risk assessment-based approach that accounts for cascading ecological changes and indirect impacts between human and environmental pressures for threatened species, for application when data-dense assessment approaches are not possible. We applied this framework to the Critically Endangered red handfish (Thymichthys politus), one of the rarest and most threatened fishes in the world, currently only known from two highly localised populations in Australia's south-east. Our approach identified the unique life history strategy of handfishes, coastal warming, indirect ecological pressures caused by recreational fishing, urban development, and poaching as the greatest current threats to the persistence of the species. Mitigation options identified to have the greatest immediate reduction in extinction risk include an ex situ captive population and release program to bolster numbers in the wild, and engagement with the commercial sea urchin fishery to help reduce impact within critical habitat. Our risk assessment process may provide a useful framework for allowing managers to make more informed and supported decisions for other species that are similarly data-poor, and when decisions would otherwise necessarily rely on best guesses that do not consider their broader ecological, environmental and anthropogenic contexts.

Fishery management in a marine protected area with compliance gaps: Socio-economic and biological insights as a first step on the path of sustainability

Overfishing is one of the main impacts on the marine environment and multiple-use Marine Protected Areas (MPAs) could be a useful tool to conserve biodiversity and promote sustainable resource exploitation. However, ensuring a high level of protection on the ground is a difficult task. This work contributes to the analysis of the causes at the root of MPAs' ineffectiveness by examining the management of Paracentrotus lividus fishery in an Italian MPA, employing a multidisciplinary approach built on biological and socio-economic competences. This sea urchin species has a determinant ecological role in structuring infralittoral benthic assemblages and is the most exploited echinoid in Europe. From 2010 to 2018, underwater sampling was conducted over 39 monitoring sites to define P. lividus spatial and temporal trends. Declared catches and semi-structured interviews with local stakeholders were used to define the socio-economical context, underline existing conflicts among them, as well as to trace the historical evolution of sea urchin fishery. The results show that the management of sea urchin fishery is not sustainable, primarily because of the stakeholders’ non-compliance with the rules. P. lividus stock is progressively declining (−73% in 9 years), showing no difference between MPA (0.5 ± 0.15 ind./m2) and control sites (0.3 ± 0.04 ind./m2). Moreover, fishermen dominate the social arena while scientists, civil society and local press have little relevance. Additionally, the untruthfulness of catch declarations was proved, the IUU fishery is relevant and the black market is hiding the actual economic value. This work offers management solutions that may be useful in other areas that show similar compliance issues.

Informing sea otter reintroduction through habitat and human interaction assessment

Sea otters Enhydra lutris have been absent from Oregon, USA, following their extirpation over a century ago. Stakeholder groups and native tribes are advocating for reintroduction to restore historic populations. We investigated the potential for successful reintroduction by: (1) estimating expected equilibrium sea otter densities as a function of habitat variables to assess sea otter habitat in Oregon; and (2) spatially relating areas of high expected densities to human activities (e.g. fisheries, recreation, vessel activity, protected areas) to anticipate potential disturbance or fishery resource competition. We estimated that 4538 (1742-8976; 95% CI) sea otters could exist in Oregon, with higher expected abundance (N = 1551) and densities (x̄ = 2.45 km-2) within the southern region. Most core habitat areas (97%), representing clusters of high expected densities, overlapped with some form of human activity. While commercial shipping and tow lanes overlapped little (1%) with core habitat areas, recreational activities (58%) and fisheries (76%) had a higher degree of overlap, posing higher disturbance risk. We anticipate higher resource competition potential with the commercial red sea urchin fishery (67% of harvest areas) than the commercial Dungeness crab fishery (9% of high-catch crabbing grounds). Our study presents the first published carrying capacity estimate for sea otters in Oregon and can provide population recovery targets, focus attention on ecological and socioeconomic considerations, and help to inform a recovery plan for a resident sea otter population. Our findings suggest current available habitat may be sufficient to support a sea otter population, but resource managers may need to further investigate and consider whether current human activities might conflict with reestablishment in Oregon, if plans for a reintroduction continue.

Retelling the History of the Red Sea Urchin Fishery in Mexico

The red sea urchin fishery has a long harvest and management history along the Northeastern Pacific coast. In Mexico, it has been commercially harvested since 1972, and although it is one of the most important fisheries in Baja California, efforts to assess the condition and dynamics of harvestable stocks have been focused on certain harvested areas with scarce fisheries independent data. Additionally, the analysis of yearly information for small geographic areas has obscured the actual status of harvested populations. This study aims to re-assess population trends, fishing effort, and catches, incorporating all available information from the last 19 years. Information was grouped based on 14 landing sites along Baja California’s Pacific coast. Length based virtual population analysis (LVPA) was implemented to estimate site-specific catch rates and densities. Red sea urchin catches / landings varied widely within and between areas. Average population density for the region reflects higher recruit values (≈2.5 urchin m-2); density of reproductive juveniles/adults averaged 0.79 (SE ± 0.04) urchins m-2; while estimated density of adults was lowest, with only 0.26 (SE ± 0.01). LVPA produced biomass estimations that double previous estimates. We suggest that the model parameters used in previous estimations might not reflect key biological traits of the red sea urchin, failing to reproduce population trends accurately. Based on current estimations, there is no apparent stock decline in areas where catches/landings are high; there, consistent settlement/recruitment may partially mitigate for fishery removals. New management measures must be adopted: maximum legal size of 110 mm, continuous fishery independent surveys, improvement on fishery logs and analysis, and tracking red sea urchin density, as means to track changes in the population that might not be so apparent when observing only catch/biomass data. Reinforce the under legal size urchins since results suggest that sites with high abundances of small urchins can support higher catches.

Going back into the wild: the behavioural effects of raising sea urchins in captivity.

Sea urchin harvesting has rapidly expanded in the last decades. Since many sea urchin species play important ecological role, large-scale commercial sea urchin fisheries can have complex effects on benthic communities. In many temperate regions, overharvesting has compromised marine ecosystems to such an extent that reintroduction of sea urchins raised in captivity may be a valid solution for the enhancement of depleted marine wild populations. In some regions of the Mediterranean Sea, improving the growth efficiency of captive sea urchin Paracentrotus lividus to be reintroduced has become a widespread practice. However, no study has yet considered the potential behavioural effects of raising sea urchins in captivity when they are introduced in the natural environment. This study provides information about the behavioural effects of captivity on P. lividus in terms of locomotion performance, a trait that can be fundamental for responding to predators and for relocation after environmental disturbances such as currents and waves. Movements of captive-born and wild sea urchins were video-recorded and compared in (i) total exposure to external cues, (ii) partial exposure to external cues and (iii) absence of external cues. Latency of locomotion, average speed and average velocity of sea urchins showed significant differences with respect to the level of exposure and their origin (i.e. wild vs. captive-born). Our results demonstrate that captive-born sea urchins in the wild showed long latency and slower locomotor performance when compared to wild sea urchins. Conversely, the straightness-of-path and locomotion direction of captive-born and wild sea urchins were similar in natural settings. Our results therefore suggest that captive-born sea urchins suffer the negative effects of captivity when introduced in a natural environment. Understanding the factors that decrease the performance of sea urchin will be important for developing procedures aimed at minimizing the negative effect of captivity before release into the wild.

Marine heat wave and multiple stressors tip bull kelp forest to sea urchin barrens

Extreme climatic events have recently impacted marine ecosystems around the world, including foundation species such as corals and kelps. Here, we describe the rapid climate-driven catastrophic shift in 2014 from a previously robust kelp forest to unproductive large scale urchin barrens in northern California. Bull kelp canopy was reduced by >90% along more than 350 km of coastline. Twenty years of kelp ecosystem surveys reveal the timing and magnitude of events, including mass mortalities of sea stars (2013-), intense ocean warming (2014–2017), and sea urchin barrens (2015-). Multiple stressors led to the unprecedented and long-lasting decline of the kelp forest. Kelp deforestation triggered mass (80%) abalone mortality (2017) resulting in the closure in 2018 of the recreational abalone fishery worth an estimated $44 M and the collapse of the north coast commercial red sea urchin fishery (2015-) worth $3 M. Key questions remain such as the relative roles of ocean warming and sea star disease in the massive purple sea urchin population increase. Science and policy will need to partner to better understand drivers, build climate-resilient fisheries and kelp forest recovery strategies in order to restore essential kelp forest ecosystem services.

Warm Water Shifts Abalone Recruitment and Sea Urchin Diversity in Southern California: Implications for Climate-Ready Abalone Restoration Planning

Nearshore kelp forest ecosystems are highly vulnerable to climate change and ocean warming, which can alter community dynamics and change the trajectory of species recovery in unpredictable ways. Abalone (Haliotis spp.) populations in the Southern California Bight (SCB) are still recovering from a combination of overfishing and disease, despite the closure of the fisheries 20 years ago and active restoration programs for abalone species in the region. For this study, abalone recruitment and sea urchin populations were surveyed in artificial habitats (16–22 m) across a spatial and temporal climatic gradient in southern California from 2010 to 2017 to inform the development of climate-ready abalone restoration programs. The SCB encompasses warm and cool islands, and experienced two periods of ocean conditions—cool (2010–2013) and warm ocean conditions (2014–2016). Dive surveys of the artificial habitats revealed that juvenile abalone recruitment remained low during the study period, suggesting that recovery is slow. Warm-water years favored recruitment of juvenile pink (Haliotis corrugata) and green abalone (Haliotis fulgens), with the highest abalone recruitment observed at Catalina Island. Endangered white abalone (Haliotis sorenseni) were not observed despite placing the artificial habitats in suitable deep rocky reefs, which is further evidence supporting their endangered species status. The coolest site, San Diego, had little abalone recruitment, with a few juvenile red abalone (Haliotis rufescens) and threaded (Haliotis kamtschatkana) abalone present. Sea urchin abundance and diversity increased during the warm period, with the largest increase at Catalina Island. During the warm period, Coronado sea urchin (Centrostephanus coronatus) increased in abundance, coincident with a decrease in the commercially valuable temperate red sea urchin (Mesocentrotus franciscanus). Potential shifts in the sea urchin assemblage to warm-water sea urchins may negatively impact recovering abalone populations and the red sea urchin fishery. Climate-ready abalone restoration will require ecosystem-based monitoring, tracking on not only abalone recruitment but also sea urchins, algal abundances, ocean temperature, and kelp forest communities as climate change may lead to complex and unexpected ecosystem interactions.

Seeking sustainability: Employing Ostrom's SESF to explore spatial fit in Maine’s sea urchin fishery

Achieving resource sustainability in complex social-ecological systems requires employing place-based management mechanisms congruent with the underlying temporal, spatial, and functional dynamics of the system in question. However, matching management to system dynamics can prove extremely challenging, as has been illustrated in Maine’s sea urchin fishery where fishery managers have struggled to resolve management spatial scale mismatch for over two decades. In Maine, the spatial scale of management far exceeds the relevant spatial dynamics of the urchin resource and leaves fine-scale urchin aggregations in a de facto open access state. These conditions facilitated the serial overharvest of urchin aggregations and resulted in the substantial loss of viable urchin habitat as overharvested areas transitioned to kelp-dominated ecosystem states that inhibit urchin recruitment. Although fishery actors contemplated adopting a number of fine-scale management alternatives to enhance social-ecological fit in the fishery, to date, no such alternatives have been employed. We adopted an ethnographic research approach and conducted semi-structured key informant interviews, document analysis of archived meeting minutes, and participant observation at co-management meetings and restoration events to explore these dynamics from the fishery’s incipience to the present. Following data analysis, we employed Ostrom’s social-ecological systems framework as a diagnostic tool to identify the factors that have influenced management spatial fit in the urchin fishery. Research findings suggest that a number of interacting variables, including harvesters’ heterogeneity and conflicting mental models of the SES, low levels of trust and social capital, and changes in the resource system following collapse impeded collective action necessary to support fine-scale management. However, changing leadership characteristics and increasing horizontal collaboration between harvesters and scientists have positively influenced governance outcomes in recent years and provide a window of opportunity to transition towards a more adaptive and collaborative governance arrangement conducive to addressing problems of fit in the urchin fishery.

A species distribution model for Paracentrotus lividus: predicted projections of habitat suitability

A species distribution model for Paracentrotus lividus: predicted projections of habitat suitability

Breeding, larval development, and growth of juveniles of the edible sea urchin Tripneustes depressus: A new target species for aquaculture in Ecuador

Sea urchin fishery has gradually expanded in different countries and territories around the world, including South America, and the sea urchin Tripneustes depressus is a feasible candidate for aquaculture. The aim of this study was to prepare a biotechnical protocol for rearing larvae and production of juveniles. Large T. depressus were collected at monthly intervals at a subtidal rocky coast off Palmar, Santa Elena, Ecuador from January 2015 to December 2017. T. depressus spawns when exposed to thermal shock in low illumination room. Seven spawning events were recorded between March and May and between July and August. On average, females spawned approximately 3.60 ± 0.83 × 107 oocytes (mean diameter: 78.4 ± 2.1 μm) and males spawned approximately 5.60 ± 1.10 × 107 spermatozoa respectively). A cohort of May 13, 2017 was followed for 250 days. Embryo and larval stages were completed within 48 h and 21 days, respectively, at 26.5 ± 0.5 °C. Larvae were fed a mixed diet of Tysochrisis lutea, Chaetoceros gracilis and Rhodomonas sp. at concentrations ranging from 2.5 × 103 to 2.0 × 104 cells /ml as they increased in size. Larvae were measured considering: Total Length (TL), Medium Base Line (MBL) and Base Width (BW). On day 2 after fertilization (AF): 311.7 ± 2.0 μm, 158.9 ± 1.0 and 270.7 ± 3.4 (n = 10), respectively. On AF16: 544.7 ± 4.0 μm, 273.6 ± 6.9 and 355 ± 3.5 (n = 10). On AF21, larval rudiment size was equal in size to that of the stomach and larvae were competent. Their body measurements, and specifically total length at that food concentration, showed no phenotypic plasticity. Thirty two days post spawning (DPS) all juveniles had open mouths and a functional gut for feeding (size: 0.40 ± 0.01 mm DT), and at DPS98 three size categories were differentiated. Sea urchin sizes by categories at DPS98 and DPS152 were, respectively: small (2.20 ± 0.1 mm DT and 23.9 ± 0.45 mm TD), medium (4.90 ± 0.08 mm DT and 33.3 ± 0.3 mm TD); and large (7.20 ± 0.11 mm DT and 43.8 ± 0.5 mm DT) with zero mortality. T. depressus reach 4 cm diameter at 188 days after metamorphosis and can reproduce after six months of life, when it reach approximately 4.2 cm diameter), although the gonads are not yet commercial in size. This protocol is an initial perfectible protocol for sea urchin aquaculturing. However, we have made recommendations for consideration that include increasing survivorship and supplying post-larvae for juvenile production.

Evaluating the promise and pitfalls of a potential climate change-tolerant sea urchin fishery in southern California.

Marine fishery stakeholders are beginning to consider and implement adaptation strategies in the face of growing consumer demand and potential deleterious climate change impacts such as ocean warming, ocean acidification, and deoxygenation. This study investigates the potential for development of a novel climate change-tolerant sea urchin fishery in southern California based on Strongylocentrotus fragilis (pink sea urchin), a deep-sea species whose peak density was found to coincide with a current trap-based spot prawn fishery (Pandalus platyceros) in the 200-300-m depth range. Here we outline potential criteria for a climate change-tolerant fishery by examining the distribution, life-history attributes, and marketable qualities of S. fragilis in southern California. We provide evidence of seasonality of gonad production and demonstrate that peak gonad production occurs in the winter season. S. fragilis likely spawns in the spring season as evidenced by consistent minimum gonad indices in the spring/summer seasons across 4 years of sampling (2012-2016). The resiliency of S. fragilis to predicted future increases in acidity and decreases in oxygen was supported by high species abundance, albeit reduced relative growth rate estimates at water depths (485-510 m) subject to low oxygen (11.7-16.9 µmol kg-1) and pHTotal (<7.44), which may provide assurances to stakeholders and managers regarding the suitability of this species for commercial exploitation. Some food quality properties of the S. fragilis roe (e.g. colour, texture) were comparable with those of the commercially exploited shallow-water red sea urchin (Mesocentrotus franciscanus), while other qualities (e.g. 80% reduced gonad size by weight) limit the potential future marketability of S. fragilis. This case study highlights the potential future challenges and drawbacks of climate-tolerant fishery development in an attempt to inform future urchin fishery stakeholders.

Exploring benefits of spatial cooperative harvesting in a sea urchin fishery: an agent‐based approach

AbstractSedentary or low‐mobility organisms show a high degree of dependency with their substrate, where its heterogeneity often determines small‐scale spatial patterns of distribution, life history traits, and fishery yields. For sea urchins, this spatial structure is usually shaped by food availability, habitat structure, individual movement, and fishery dynamics. All of these have a significant impact on their physiological and reproductive status and in particular on their gonadal content. These patterns are of particular interest considering that the sea urchin fishery is a roe fishery where marketability depends on gonad yield and quality, which in turn is related to spatial and temporal variations in associated kelp beds. Thus, better gonad quality and yields generate higher profits for both fishers (divers) and processors. However, competition among divers within a non‐cooperative system creates a “race for shellfish” precluding higher gonad yields per unit of effort. A spatially explicit agent‐based model for the San Diego, California red sea urchin (Strongylocentrotus franciscanus) fishery was developed in order to assess the benefits of cooperative harvesting by depicting spatial and temporal variations in fishery yields. A cooperative harvesting scenario where divers consistently target those areas with higher yields avoiding low‐quality sea urchins was compared against a non‐cooperative situation where divers harvest at random or based only on densities of sea urchins. Sea urchin population at the end of the simulation period was 20% higher for the most cooperative scenario compared to the non‐cooperative fishery. Further, for the most cooperative scenario where information sharing among divers is greatest and harvest is coordinated, sea urchin catches were at least 10% higher and gonad yield 35% higher than in the non‐cooperative scenario. In this model, information sharing and organized harvesting typical of well‐functioning cooperatives allowed fishers to optimize the use of the resource in terms of higher gonad yields per unit of effort while maintaining the productivity of the stock. This study also highlights the importance of community‐based management (i.e., collaborative efforts in assessment, management, and governance of fisheries between fishers, scientists, and managers) toward improving fisheries sustainability.

Hard time to be parents? Sea urchin fishery shifts potential reproductive contribution of population onto the shoulders of the young adults.

BackgroundIn Sardinia, as in other regions of the Mediterranean Sea, sustainable fisheries of the sea urchin Paracentrotus lividus have become a necessity. At harvesting sites, the systematic removal of large individuals (diameter ≥ 50 mm) seriously compromises the biological and ecological functions of sea urchin populations. Specifically, in this study, we compared the reproductive potential of the populations from Mediterranean coastal areas which have different levels of sea urchin fishing pressure. The areas were located at Su Pallosu Bay, where pressure is high and Tavolara-Punta Coda Cavallo, a marine protected area where sea urchin harvesting is low.MethodsReproductive potential was estimated by calculating the gonadosomatic index (GSI) from June 2013 to May 2014 both for individuals of commercial size (diameter without spines, TD ≥ 50 mm) and the undersized ones with gonads (30 ≤ TD < 40 mm and 40 ≤ TD < 50 mm). Gamete output was calculated for the commercial-size class and the undersized individuals with fertile gonads (40 ≤ TD < 50 mm) in relation to their natural density (gamete output per m2).ResultsThe reproductive potential of populations was slightly different at the beginning of the sampling period but it progressed at different rates with an early spring spawning event in the high-pressure zone and two gamete depositions in early and late spring in the low-pressure zone. For each fertile size class, GSI values changed significantly during the year of our study and between the two zones. Although the multiple spawning events determined a two-fold higher total gamete output of population (popTGO) in the low-pressure zone, the population mean gamete output (popMGO) was similar in the two zones. In the high-pressure zone, the commercial-sized individuals represented approximatively 5% of the population, with almost all the individuals smaller than 60 mm producing an amount of gametes nearly three times lower than the undersized ones. Conversely, the high density of the undersized individuals released a similar amount of gametes to the commercial-size class in the low-pressure zone.DiscussionOverall, the lack of the commercial-size class in the high-pressure zone does not seem to be very alarming for the self-supporting capacity of the population, and the reproductive potential contribution seems to depend more on the total density of fertile sea urchins than on their size. However, since population survival in the high-pressure zone is supported by the high density of undersized sea urchins between 30 and 50 mm, management measures should be addressed to maintain these sizes and to shed light on the source of the larval supply.

Profitability and sustainability of edible sea urchin fishery in Sardinia (Italy)

Sea urchin (Paracentrotus lividus) fishery is intensively practiced in several areas of the Mediterranean basin. In Sardinia, as well as other Mediterranean countries, sea urchin is a basic ingredient for several dishes due to the delicacy of its gonads (roe), and demand is constantly increasing. Restrictions have been implemented in order to minimise the risk of overexploitation, however, these measures might jeopardize economic convenience in sea urchin harvesting. This paper estimates economic convenience within the edible sea urchin fishery in Sardinia. It aims to determine whether both profitability and sustainability, in terms of the preservation of sea urchin stock, can be guaranteed by actual policy regulation. We found high variability in terms of captures and profitability among firms, and a considerable degree of this variability is the result of technological differences between fishing methods. Analysis also suggests that a slight increase in allowed captures should generate a more than proportional increase in profits. This evidence gives some useful suggestions for improving the efficacy of policies in affecting the economic and environmental sustainability of the Mediterranean sea urchin fishery.

Temporal variability of spawning in the sea urchin Paracentrotus lividus from northern Spain

Temporal variability of spawning in the sea urchin Paracentrotus lividus from northern Spain

Low temperature tolerance of a sea urchin pathogen: Implications for benthic community dynamics in a warming ocean

Disease outbreaks in the sea urchin Strongylocentrotus droebachiensis on the Atlantic coast of Nova Scotia have increased in frequency over the last 35years, in association with increasing sea temperatures and strong storm events. Previous studies suggest that the causative agent of disease, the pathogenic amoeba Paramoeba invadens, cannot withstand winter sea temperatures on this coast, and may be an alien species. Consequently, recurrent epizootics result from repeated introductions of this pathogen, possibly due to advection or vertical mixing associated with storm events. Here we test an alternative hypothesis that P. invadens has established resident populations, either through physiological adaptation to low winter temperatures, or because winter minima have increased since 1980. To test this hypothesis, we manipulated culture temperatures of P. invadens isolated from moribund sea urchins during a disease outbreak in 2012. Specific growth rates of P. invadens in culture at 0.5 to 18.0°C were similar to those observed in the early 1980s, providing no evidence of physiological adaptation. P. invadens declined to extinction in culture after ~1month at 0.5°C and 2.0°C, but survived for 3months at 3.5°C, as indicated by recovery of cultures following transfer to optimal temperature. These results indicate a lower temperature tolerance threshold around 2–3°C, which is consistent with observational data of recurrent mass mortalities of sea urchins in 1983 and 2012 in the absence of a storm but following relatively warm winters. A trend of increasing minimum temperatures in winter indicates that P. invadens could undergo a range expansion to establish a resident population in Nova Scotia within 1–2 decades. This is expected to increase the resilience of the kelp-bed state of the benthic ecosystem but result in the complete collapse of the sea urchin fishery.