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Harvesting Effects on Paracentrotus lividus Population Structure: A Case Study from Northwestern Sardinia, Italy, before and after the Fishing Season

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Antonio Pais at Università degli Studi di Sassari
Antonio Pais
Simonetto Serra at Agenzia della Regione Sardegna per la ricerca scientifica
Simonetto Serra
Gianni Meloni
Gianni Meloni
Gianni Meloni
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Sara Saba
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Abstract

The edible sea urchin Paracentrotus lividus is commercially exploited in many European countries. In recent years, however, its stocks have shown a large reduction in several regions because of overfishing. This paper reports the effects of harvesting on P. lividus population structure in shallow rocky reefs from a central-western Mediterranean area where this activity is intensively practiced. Density, size (test diam), and biomass of sea urchin were assessed in October 2004 (just before the fishing season) and in May 2005 (immediately after the fishing season) at two locations where intense P. lividus harvest occurs and at two controls within an adjacent Marine Protected Area (MPA) where P. lividus harvest is prohibited. Density, size, and average biomass of P. lividus were significantly higher at the protected areas than at the exploited ones. In particular, large-sized specimens (test diam >5 cm) were notably less abundant at the fished locations; however, very similar results were detected for both the periods examined (i.e., before and after the fishing season), suggesting that effects of pressing activity of harvest through the past years may have produced effects much more evident than those attributable to the single fishing season. These results reveal the existence of a heavy-fishing impact on P. lividus in northwestern Sardinia and the urgent need of regulating its harvesting to prevent severe direct effects on its populations.
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Harvesting Effects on Paracentrotus lividus Population
Structure: A Case Study from Northwestern Sardinia, Italy,
before and after the Fishing Season
Antonio Pais
{
, Simone Serra
{
, Gianni Meloni
{
, Sara Saba
{
, and Giulia Ceccherelli
{
{
Sezione di Acquacoltura e Gestione delle
Risorse Acquatiche
Dipartimento di Scienze Zootecniche
Universita
`di Sassari, Via De Nicola 9
07100 Sassari, Italy
pais@uniss.it
{
Dipartimento di Scienze Botaniche
Ecologiche e Geologiche, Via Piandanna 4
07100 Sassari, Italy
ABSTRACT
PAIS, A.; SERRA, S.; MELONI, G.; SABA, S., and CECCHERELLI, G., 2012. Harvesting effects on Paracentrotus lividus
population structure: A case study from northwestern Sardinia, Italy, before and after the fishing season. Journal of
Coastal Research, 28(3), 570–575. West Palm Beach (Florida), ISSN 0749-0208.
The edible sea urchin Paracentrotus lividus is commercially exploited in many European countries. In recent years,
however, its stocks have shown a large reduction in several regions because of overfishing. This paper reports the effects
of harvesting on P. lividus population structure in shallow rocky reefs from a central-western Mediterranean area where
this activity is intensively practiced. Density, size (test diam), and biomass of sea urchin were assessed in October 2004
(just before the fishing season) and in May 2005 (immediately after the fishing season) at two locations where intense P.
lividus harvest occurs and at two controls within an adjacent Marine Protected Area (MPA) where P. lividus harvest is
prohibited. Density, size, and average biomass of P. lividus were significantly higher at the protected areas than at the
exploited ones. In particular, large-sized specimens (test diam .5 cm) were notably less abundant at the fished locations;
however, very similar results were detected for both the periods examined (i.e., before and after the fishing season),
suggesting that effects of pressing activity of harvest through the past years may have produced effects much more
evident than those attributable to the single fishing season. These results reveal the existence of a heavy-fishing impact
on P. lividus in northwestern Sardinia and the urgent need of regulating its harvesting to prevent severe direct effects on
its populations.
ADDITIONAL INDEX WORDS: Echinoderm fisheries, Paracentrotus lividus, Mediterranean Sea, Sardinia.
INTRODUCTION
Commercial fisheries have induced a dramatic depletion of
global resources during the last decades masked by technolog-
ical improvement, geographic range expansion, and exploita-
tion of species lower in the food web (Pauly et al., 2002). In
particular, overexploitation of marine invertebrates has in-
creased primarily for those species whose market value is
sufficiently high, which encourages illegal fishing, or in areas
where fishing effort is not adequately managed and monitored
(Jamieson, 1993).
Different species of sea urchins are commercially exploited
around the world (Keesing and Hall, 1998), although in recent
years increased demand has led to overfishing, and, in some
countries, wild stocks have diminished (Sloan, 1985). This
phenomenon was well documented for a number of species such
as the green sea urchin Strongylocentrotus droebachiensis from
the coast of Maine (western Atlantic; Chen and Hunter, 2003),
the red sea urchin S. franciscanus from the San Juan Islands
(northern Pacific; Carter and VanBlaricom, 2002; Pfister and
Bradbury, 1996), the short-spined sea urchin S. intermedius
from the Japanese coast (eastern Pacific; Agatsuma, 2001 and
references therein), and the white-spined sea urchin Trip-
neustes ventricosus from Saint Lucia Island (Caribbean Sea;
Smith and Berkes, 1991).
The edible sea urchin Paracentrotus lividus (Lamarck, 1816)
is widely distributed in the Mediterranean Sea and along the
northeastern Atlantic coast (Boudouresque and Verlaque,
2001). It lives on rocky bottoms and in Posidonia oceanica
seagrass beds from shallow waters down to about 20 m depth.
This species has an important commercial value for its gonads
(roe), with a high-market demand in many Mediterranean
regions (Re
´gis, Pe
´re
`s, and Gras, 1986) and in some other non-
Mediterranean European areas (Barnes and Crook, 2001;
Byrne, 1990). In recent years, however, its stocks have shown
a large reduction in several European countries because of
overfishing (Boudouresque and Verlaque, 2001 and references
therein). In Italy, P. lividus fishing activities are very common
in a number of southern regions (Guidetti, Terlizzi, and Boero,
2004; Tortonese, 1965), particularly in Sardinia (central-
western Mediterranean). In this latter region, despite the
harvesting of this echinoid being regulated (i.e., fishing
DOI: 10.2112/JCOASTRES-D-10-00119.1 received 17 August 2010;
accepted in revision 23 December 2010.
This study was funded by the Italian M.I.U.R. (project F.A.R. ex
60%).
’Coastal Education & Research Foundation 2012
Published Pre-print online 21 March 2011
Journal of Coastal Research 28 3 570–575 West Palm Beach, Florida May 2012
... Moreover, the class frequencies from 27 to 41 mm represented about 81.44% of the total collected catch. This finding is in agreement with Pais et al. (2012) and Bertocci et al. (2014) who reported that the number of large-size individuals (exceeding 50 mm) in the fishery of P. lividus in Sardinia and the north of Portugal, respectively, was scant. These large sizes were found exclusively in protected areas or inside marine reserves where fishing activities were prohibited (Pais et al., 2012). ...
... This finding is in agreement with Pais et al. (2012) and Bertocci et al. (2014) who reported that the number of large-size individuals (exceeding 50 mm) in the fishery of P. lividus in Sardinia and the north of Portugal, respectively, was scant. These large sizes were found exclusively in protected areas or inside marine reserves where fishing activities were prohibited (Pais et al., 2012). Furthermore, the unregulated intense harvesting of P. lividus in shallow Mediterranean rocky reefs decreased the mean size and biomass of their population (Guidetti et al., 2004). ...
... The present work also suggests the urgent need of creating a harvest refuge for P. lividus population to secure high population density in a protected area, as recommended by Ouréns et al. (2014). Along the same line, Pais et al. (2012) and Bertocci et al. (2014) suggested that the Marine Protected Areas (MPAs) and the fishery restrictions cause a positive effect on biomass, size, and density of P. lividus, leading to protecting and sustaining their fishery. These authors expressed the need for further studies on the echinoids' fisheries ecology, especially in the Mediterranean region where edible sea urchins are harvested intensely. ...
View
... The gonads, the only edible part of the sea urchin (O'Hara and Thoŕarinsdottir, 2021), contain high-quality proteins that are also rich in nutrients (Ciriminna et al., 2021) and have high commercial value. However, the number of wild sea urchins has been drastically reduced due to overfishing (Pais et al., 2011;Lawrence, 2013) and declining food resources (Yeruham et al., 2019). Currently, many studies on sea urchins have focused on reproduction (Hassan et al., 2022), food resources (Takagi et al., 2022) and the effects of environmental factors (Chi et al., 2021). ...
Assessment of annual variability in the population status and reproductive cycle of purple sea urchins (Heliocidaris crassispina, Agassiz, 1864) in Daya Bay, China
Article
Full-text available
  • Jan 2024
The purple sea urchin (Heliocidaris crassispina) is one of the main drivers of ecosystem dynamics, and its reproductive cycle plays an important role in population structure and size variability. In this study, we analyzed the population structure, gonadal developmental characteristics, reproductive cycle and other factors influencing wild purple sea urchins from December 2021 to November 2022 in Daya Bay, Guangdong, China. The results showed that purple sea urchins showed an allometric growth pattern, there were obvious seasonal variations in the population size, and fishing pressure reduced the sea urchin populations; two-factor analysis of variance (ANOVA) and correlation analyses showed negative correlations between month (M), test diameter (TD), weight (W) and gonadal index (GI) (P> 0.01), and a positive correlation between TD, weight (W), and GI (P<0.01); the gonadal development process can be divided into recovery, growth, prematuration, maturation, and late discharge, with almost synchronous development of male and female gametes; the spawning period is from April to November, which is longer than in the temperate zones, showing two spawning peaks in April and August. The time of spawning is influenced by temperature and food. Data on the breeding cycle of sea urchins in Daya Bay were obtained in this study. This information can offer theoretical assistance in the preservation and management of both artificial nurseries and wild resources.
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... This study also recontextualizes the Algerian coast contamination throughout the geographical distribution of P. lividus from the Mediterranean Sea to the Northeastern Atlantic. This study also evaluates the health risk of its gonad consumption, considering the increasing commercial interest of this species in Algeria and its already overexploitation in several countries: Ireland (Barnes et al., 2002), France (Patrissi et al., 2014), Spain (Fernández-Boán et al., 2012;Guinda et al., 2017), Portugal (Bertocci et al., 2014(Bertocci et al., , 2018, Italy (Gianguzza et al., 2007;Guidetti et al., 2004;Pais, 2011;Pais et al., 2007), Croatia (Sanja et al., 2010) and Greece (Vafidis et al., 2019). Specific objectives are: (i) to study the seasonal dynamics of seven MTEs (Cd, Pb, Fe, Cu, Zn, Ni and Co) in sea urchin gonads in relation to the physiology of the species; (ii) to perform intraspecific comparisons with previous regional studies in order to establish a complete comparative mapping at the scale of distribution of the species, and to rank MTEs in order of environmental concern according to the overall spatial variability of their concentrations; iii) to enrich the available data on potential human health risks associated with sea urchin consumption with data from the Algerian coast. ...
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... In this context, the utilization of sea urchin spermatozoa as a model for ecotoxicological tests can be considered a good tool for the evaluation and estimation of the deleterious effect of nanoparticles used in water remediation [36]. Therefore, it will be necessary to deepen the studies on the possible effects of NPs on fertilization and the first stages of development of P. lividus that is already threatened by various xenobiotics and contaminants present in the marine environment, through overfishing and habitat destruction [37][38][39]. Lastly, ecotoxicological tests should be performed on each newly synthetized compound before its introduction into marine environments to evaluate the associated risks for marine life. ...
Spermiotoxicity of Nano-TiO2 Compounds in the Sea Urchin Paracentrotus lividus (Lamarck, 1816): Considerations on Water Remediation
Article
Full-text available
  • Feb 2023
Despite the great utility of nanoparticles (NPs) in water remediation, their effects on marine ecosystems are unknown and unpredictable. The toxicity of the most used nanoparticles, such as ZnO, Ag, and TiO2 on the purple sea urchin, Paracentrotus lividus (Lamarck, 1816), has been demonstrated by several authors. The aim of this study was to evaluate the effects of TiO2 sol-gel and TiO2-rGO nanocompounds on both vitality and motility of spermatozoa of P. lividus. The spermatozoa were exposed at different times (30 and 60 min) and concentrations (10, 20, 40 µg/mL) of both nano-TiO2 compounds. The results clearly showed a decrease in both vitality and motility of P. lividus spermatozoa exposed. In particular, vitality and motility were inversely related to both exposure time and concentration of TiO2 sol-gel and TiO2-rGO nanocompounds.
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... In fact, P. lividus is an important fishing/ harvesting resource in some European countries, because its gonads (roe) constitute a greatly appreciated and highly profitable seafood delicacy (Gianguzza et al., 2006;Ouréns, 2013;Bertocci et al., 2014;Boudouresque and Verlaque, 2020). For this reason, P. lividus has been intensively harvested in diverse countries, such as Ireland (Byrne, 1990; Barnes et al., 2002), France (Allain, 1975;Le Gall, 1987), Spain (Palacín et al., 1998b;Fernández-Boán et al., 2012;Guinda et al., 2017), Portugal (Bertocci et al., 2014(Bertocci et al., , 2018, Italy (Guidetti et al., 2004;Gianguzza et al., 2006;Pais et al., 2007Pais et al., , 2012, Croatia (Tomsic et al., 2010) and Greece (Vafidis et al., 2019). Consequently, in some areas along the Atlantic and Mediterranean, intense harvesting of P. lividus led to overexploitation or even collapse of natural populations (Allain, 1975;Le Gall, 1987;Byrne, 1990;Boudouresque and Verlaque, 2020). ...
Morphometric relationships, relative growth and roe yield of the sea urchin (Paracentrotus lividus) from the Portuguese coast
Article
  • Mar 2022
Sea urchin (Paracentrotus lividus) populations from the northwestern (Carreço) and southwestern (Aljezur) coasts of Portugal were surveyed to analyse and compare their morphometric relationships, relative growth (isometry vs. allometry) and roe yield. Specimens were hand-collected from intertidal rock pools and sampled monthly during two consecutive years (November 2010 – November 2012). Overall, 1220 P. lividus larger than 40 mm in test diameter (542 from Carreço and 678 from Aljezur) were analysed during the study period. Morphometric relationships established between specimen size (test diameter, height and volume) and weight (total and gonad weight) were statistically significant and displayed high correlation coefficients (r = 0.484 – 0.974), with allometric coefficients ranging from b = 0.962 to 1.239 (linear variables) and from b = 2.541 to 3.437 (linear and ponderal variables). Sea urchins mean roe yield was significantly higher in Carreço (7.5 ± 3.1%) than in Aljezur (6.8 ± 3.5%) and varied depending on the sampling month. The present data on morphometric relationships, relative growth and roe yield was duly compared with previous studies available on these topics, through an exhaustive review covering the distributional range of P. lividus along the Atlantic Ocean and Mediterranean Sea.
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... Sea urchin gonads, also known as roe, are a prized seafood product worldwide. Consequently, a dramatic reduction of natural stocks of sea urchin commercial species, due to uncontrolled over-exploitation, has been recently observed (Lawrence, 2013;Pais et al., 2011;Yeruham et al., 2019). In many countries of the Mediterranean area, Paracentrotus lividus (Lamarck, 1816) is the most exploited sea urchin for commercial purposes, with substantial detrimental impacts on local populations and the whole ecosystems (Guidetti et al., 2004;Pais et al., 2007). ...
Turning waste into gold: Sustainable feed made of discards from the food industries promotes gonad development and colouration in the commercial sea urchin Paracentrotus lividus (Lamarck, 1816)
Article
Full-text available
  • Nov 2021
Development of sustainable aquaculture practices is a suitable solution to reduce the pressure on overexploited stocks of the Mediterranean sea urchin, Paracentrotus lividus, and to respond to the increasing market demand. To move forward the Blue Growth and following the principles of circular economy, a three-month feeding experiment was conducted to test a sustainable feed based on food processing discards on sea urchins. Two feed formulations differing on the proportions of the two main ingredients (endive outermost leaves and European anchovy discards in a ratio of 60:40 and 80:20 respectively) were prepared and tested on P. lividus gonad yield, development and quality. The results were compared with those of wild sea urchins to assess the differences with natural patterns. Both feed formulations promoted gonad growth resulting in a significantly higher percentage increase in gonad biomass compared with wild specimens (490%, 330% and 78% increase in gonad weight in the feed 60/40, 80/20 and wild sea urchins respectively). Similarly, GSI of reared sea urchins varied by about 3–12% and 14% for sea urchins fed with feeds 80/20 and 60/40 respectively, while that found in wild sea urchins varied by about 3–5%. Gonad development was also boosted by the provision of the sustainable feed, as sexual maturation was faster in reared specimens than in wild ones. At the end of the trial, reared sea urchins showed also a very high (> 90%) frequency of marketable gonad colour. Lastly, the formulation with a more balanced vegetal/animal ratio (feed 60/40) gave the best results overall, combining the highest GSI and the best gonad colouration. Outcomes of this study confirm the suitability of food processing discards as ingredients for sea urchin feeds, although further research is needed to evaluate the effects on nutritional quality and organoleptic features of sea urchin gonads.
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... As a direct consequence of the growing human population in world coastal areas, intertidal benthic organisms are increasingly subject to harvesting for commercial, recreational and food purposes (Hockey and Bosman, 1986;Castilla and Bustamante, 1989;Underwood, 1993b;Lasiak, 1998;Gilby et al., 2020), trampling (Brosnan and Crumrine, 1994;Plicanti et al., 2016), and a range of indirect effects mediated by the removal of species that play key ecological roles (Lindberg et al., 1998;Castilla, 1999;Martins et al., 2008). For example, similarly to many other sea urchin species that are exploited worldwide (Andrew et al., 2002;Micael et al., 2009), the purple sea urchin Paracentrotus lividus (Lamarck, 1816) is intensively harvested in Europe at several locations both in the Mediterranean Sea and the Atlantic Ocean (Byrne, 1990;Barnes and Crook, 2001;Pais et al., 2012;Bertocci et al., 2014Bertocci et al., , 2018, which led to signs of overexploitation of many stocks (Boudouresque and Verlaque, 2007;Fernández-Boán et al., 2012;Ouréns et al., 2014). This is of concern not just in terms of fishery-related and economic issues, but also due to the role of P. lividus and other urchins species as bioengineers able, through their intense grazing activity when at large densities, to drive shifts from diverse assemblages dominated by erect macroalgae to less productive habitats, such as barren assemblages dominated by upright and encrusting coralline algae (Hereu et al., 2004;Jacinto et al., 2013;Ouréns et al., 2014;Filbee-Dexter and Wernberg, 2018;Ling et al., 2019). ...
Resurvey of sea urchins and mussels at protected and harvested shores a decade after: a BEYOND-BACI approach
Article
  • May 2021
  • MAR ENVIRON RES
Comparing temporal patterns of distribution and abundance of target organisms between protected and harvested shores is essential to assess the extant effectiveness of marine protected areas (MPAs) and whether it is maintained through time. By means of an adapted Beyond-BACI approach, we compared the short- and long-term patterns of variation in the abundance of the sea urchin Paracentrotus lividus and the mussel Mytilus galloprovincialis at a protected shore (within the Parque Litoral Norte MPA, Portugal) and at three adjacent shores subject to intense harvesting over a decadal interval. Despite the existence of the MPA for more than 30 years, we did not obtain clear evidence of its persistent or recent effectiveness on intertidal species of commercial interest. We suggest the need for refining management options along the northern Portuguese coast, possibly by better enforcing current regulations and reconsidering the present design of protection schemes. Moreover, the adopted analytical approach may represent a methodological reference for similar investigations in systems where the perturbation of interest (protection or disturbance) would not occur at a given time during the course of the study, but has been operating since before the first sampling occasion and maintained until subsequent surveys.
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... However, there is sufficient evidence that fishing pressure has depleted populations in some sea urchin species as a consequence of overfishing and the expansion of harvesting areas (Sloan, 1985;Schebling and Mladenov, 1987;Johnson et al., 2012). Due to these trends, there is a rising concern about the direct effect of fishing and its potential impacts on natural sea urchin populations (Pfister and Bradbury, 1996;Lau et al., 2011;Pais et al., 2012;Bertocci et al., 2018). ...
Impacts of fishing on the Caribbean white sea urchin, Lytechinus variegatus, in Margarita Island, Venezuela
Article
  • Mar 2021
  • MAR ENVIRON RES
The Caribbean white sea urchin, L. variegatus, is locally harvested in Margarita Island and other locations of southeastern Venezuela. The recent reduction of densities raises concerns about potential impacts for overfishing. Densities of L. variegatus were estimated at impacted and control locations between late-2012 and mid-2015 to test temporal changes, comparing with 1997-1998 estimations, the effect of seasonal closure on resource recovery and the effect of local expansion. The results suggest that, after a period of fourteen years, an important decrease in L. variegatus densities occurred, as well as a lack of population recovery in fishing areas during seasonal closures. Furthermore, during the monitoring program, it was observed fishing activities in one control location that subsequently showed clear patterns of population depletion, like other impact locations. Fishing impact on L. variegatus populations is severe, persistent and expands over time without evidence of recovery, therefore it is expected that local populations of L. variegatus would collapse under current exploitation levels. However, due to the L. variegatus life history and its distribution range, recovery of impacted populations could be possible via recruitment of planktonic larvae if effective management actions are imposed. It is recommended to exercise more regulations on fishing activities and to execute management measures that allow recovering the stocks to maintain local populations of sea urchin.
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Intensive sea urchin harvest rescales Paracentrotus lividus population structure and threatens self-sustenance
Article
Full-text available
  • Nov 2023
The harvest of the edible sea urchin Paracentrotus lividus is intensively practiced in some regions of the Western Mediterranean Sea. The removal of the largest individuals can determine an overall reduction in population size and a size class truncation that can lead to a drastic drop the self-sustenance. The aim of this study is to evaluate the variability of the population reproductive potential across 5 years in one of the main harvest hotspots of Sardinia (Western Mediterranean Sea). The breeding stock consists of commercial and under-commercial size individuals which were sampled on a monthly basis to estimate their GonadoSomatic Index (GSI) and the Individual Gamete Output (IGO). In addition, the reproductive potential of the population-Total Gamete Output (TGO)-was calculated across the 5-year period in relation with the variation of the density of the breeding stock. During the last year, the reproductive potential was also estimated in a well-conserved population of a nearby Marine Protected Area. No significant variability in GSI and IGO was found over the 5 years nor when compared with the ones of protected population in the last year. However, the intensive harvest drastically rescaled the population body-size: although density of the commercial size class remained low, density of the under-commercial size-class halved from the beginning to the end of the study. Accordingly, the proportional decrease of their gamete output contribution led to a 40% loss of the reproductive potential of the whole population in the 5-year period. Interestingly, despite the loss of reproductive potential due to the decrease of the breeding stock density, the average values of IGO slightly increased across the years leading to the highest Annual Gamete Output (AGO) during the fourth year of sampling. This positive pattern could suggest a mechanism of reproductive investments of the survivors in terms of gonad production rate or increase in spawning intensity. This work provides evidence of the direct effect of size-selective harvesting on the rapid loss of population self-sustenance. Furthermore, it lays new prospective for future research of the indirect effects of the rescaling population body-size in functional traits of the sea urchin.
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Population Density, Reproduction Cycle and Nutritional Value of Sphaerechinus granularis (Echinodermata: Echinoidea) in an Oceanic Insular Ecosystem
Article
Full-text available
  • Jan 2022
Sea urchins play an important role in island coastal ecosystems as keystone species and as potential resources for harvesting and aquaculture. In Southern Europe, the most valuable and harvested species is the European purple sea urchin Paracentrotus lividus, but there is a growing interest to explore other edible species like the blunt sea urchin Sphaerechinus granularis. The echinoderms biodiversity of Madeira archipelago was previously described, but their local habitat, population densities and size distribution, important to establish their harvest and aquaculture potential, are poorly known. The present study aimed to evaluate S. granularis population in the oligotrophic and narrow insular shelf of Madeira archipelago, mainly regarding its habitat, densities, reproduction season and roe marketable characteristics. Sphaerechinus granularis was found in low densities (0.01 ind./m2) from shallow to deep reefs (5–30 m). The highest densities occurred in shallow waters and breakwaters in association to encrusting algae, turf and erect brown macroalgae. Here, the low primary productivity ecosystem influenced the long reproductive season of the local population. This population showed a relatively high gonadosomatic index (maximum GI of 8), high gonad weight (5.00–12.19 g) with high proportion of bright yellow and orange gonads (37.5–60%) between February and November. Additionally, the high level of total carotenoids, the high PUFA (particularly EPA) content, and the ratio n-6/n-3 close to one support the high nutritional value of S. granularis roe. The trend of incremental GI between September and November and the increasing content of PUFA in autumn suggests this could be the preferential harvesting season. This information is key to evaluate a sustainable exploitation of this living marine resource.
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Effects of experimental harvest on red sea urchins (Strongylocentrotus franciscanus) in northern Washington
Article
Full-text available
  • Oct 2002
  • FISH B-NOAA
Commercial harvest of red sea urchins began in Washington state in 1971. Harvests peaked in the late 1980s and have since declined substantially in Washington and other areas of the U.S. west coast. We studied effects of experimental harvest on red sea urchins in San Juan Channel (SJC), a marine reserve in northern Washington. We recorded changes in density and size distribution of sea urchin populations resulting from three levels of experimental harvest: 1) annual size-selective harvest (simulating current commercial urchin harvest regulations), 2) monthly complete (non-sizeselective) harvest, and 3) no harvest (control) sites. We also examined re-colonization rates of harvested sites. The red sea urchin population in SJC is composed of an accumulation of large, old individuals. Juvenile urchins represent less than 1% of the population. Lower and upper size limits for commercial harvest protect 5% and 45% of the population, respectively. Complete harvest reduced sea urchin densities by 95%. Annual size-selective harvest significantly decreased sea urchin densities by 67% in the first year and by 47% in the second year. Two years of size-selective harvest significantly altered the size distribution of urchins, decreasing the density of legal-size urchins. Recolonization of harvested sites varied seasonally and occurred primarily through immigration of adults. Selective harvest sites were recolonized to 51% and 38% of original densities, respectively, six months after the first and second annual harvests. Yields declined substantially in the second year of size-selective harvest because of the fishing down of the population and because of low re-colonization rates of harvested sites. We recommend that managers consider the potential efficacy of marine harvest refuges and reevaluate the existing upper and lower size limits for commercial harvest to improve long-term management of the sea urchin fishery in Washington.
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Review of harvests and status of world sea urchin fisheries points to opportunities of aquaculture
Article
Full-text available
  • Dec 1998
It is more than a decade since there was an attempt to review sea urchin harvests and the status of sea urchin fisheries around the world. Much of this information resides in gray literature and unpublished reports, some of which are difficult to access. For many countries, only export figures are available, leaving uncertainty over total harvests and domestic consumption. Present world production is around 117,000 tonnes, most of which is imported into Japan, where local production has declined, and there are now attempts for this to be supported by stock enhancement methods. The world's major producers of sea urchins are the United States, Chile, and Japan. Catches of sea urchins in these and most other producing countries are declining or have reached their peak. Although several countries have underexploited sea urchin resources, these are insignificant in terms of world demand. The only countries with significant potential for expansion of sea urchin fisheries are perhaps the Russian Federation, Canada, and the two Koreas, but information from some of these regions is sparse, and there are a range of obstacles to sustainable and cost-effective exploitation. Given the general decline in fisheries in major producing countries and the continued strong demand for sea urchin roe, there are emerging opportunities for sea urchin aquaculture and roe enhancement in many countries.
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Temporal variability in abundance of the sea urchins Paracentrotus lividus and Arbacia lixula in the northwestern Mediterranean: Comparison between a marine reserve and an unprotected area
Article
Full-text available
  • Jul 1998
Sea urchin populations were monitored in the Medes Islands Marine Reserve (NW Mediterranean) and an adjacent unprotected area in order to (1) describe temporal variability in abundance and population size-structure of sea urchins within each area (from 1991 to 1997), and (2) to compare these areas to investigate the role of fish predation level in determining sea urchin population structure over time (from 1995 to 1997). Abundance of the sea urchin Paracentrotus Lividus (Lamarck) was monitored at 7 sites (4 inside and 3 outside the reserve), and 2 distinct habitats (fields of big boulders and vertical walls). P. Lividus exhibited significant variability in density over time on boulders, both inside and outside the reserve, whereas its density did not vary significantly on vertical walls. P. lividus populations differed significantly in size-structure across sites, varying from unimodal to bimodal among sites and years. Density and mean size of P. lividus were not significantly different between the protected and the unprotected area in either of the 2 habitats. Abundance of the sea urchin Arbacia lixula (L.) was monitored from 1995 to 1997 on vertical walls and boulders (4 sites inside and 3 sites outside the reserve). Density of A. lixula differed significantly over time on boulders, but it did not on walls. On vertical walls, density and mean size of A. lixula were not significantly different between areas in both habitats. This study shows that in the Medes Islands region, sea urchins exhibit striking short-term fluctuations in abundance, which can lead to misinterpretation of larger-scale temporal patterns. The comparison between the protected and the unprotected area does not support the hypothesis of fish predation as the most important factor affecting P. lividus populations in the Medes Islands, as patterns of lower sea urchin density relative to the unprotected area nearby were not maintained over time. These facts indicate that factors other than fish predation are very important in determining sea urchin population structure in the northwestern Mediterranean.
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Harvesting Red Sea Urchins: Recent Effects and Future Predictions
Article
Full-text available
  • Feb 1996
The red sea urchin, Strongylocentrotus franciscanus, is a conspicuous member of subtidal communities in the north Pacific. Within the last decade, this ecologically important species has been exposed to intense harvesting for the first time ever. Analysis of population census data suggest that harvestable size urchins have rapidly declined in shallow regions while catch-per-effort and landings data suggest that divers have maintained high landings by exploiting more distant and difficult fishing areas, including deeper areas. We present a size-structured model for the red sea urchin both to estimate what previous levels of harvesting mortality were and to explore what effect future harvesting strategies might have on population trajectories. Using population census data, we explore three models: one that would result in an equilibrial population size in the absence of fishing, one that includes positive density dependence (an "Allee effect"), and one that incorporates realistic variability in recruitment. Our principal findings are that annual fishing mortality levels that best fit the observed census data in the past (1984-1993) were 0.38-0.49 and represent a 70-90% decrease in the survivorship of harvestable urchins in the years of fishing. Under a variety of fishing strategies, 100-yr projections indicated that the inclusion of an Allee effect or variability in recruitment could drive the harvestable population to <50% of present estimated population size at relatively low annual fishing mortality values. Our simulations also indicated that, although a yearly fishery would have higher yields, a rotational fishery would maintain populations at a level less likely to cause irreversible decline. The wealth of empirical evidence that sea urchins are an important component of nearshore communities should encourage management strategies that emphasize long-term population viability.
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MORPHOMETRIC RELATIONSHIPS AND ANNUAL GONAD INDEX OF THE EDIBLE SEA URCHIN PARACENTROTUS LIVIDUS FROM NORTH WESTERN SARDINIA
Article
Full-text available
  • Jan 2006
Weight/diameter, weight/height and height/diameter morphometric relationships were calculated for a shallow rocky Paracentrotus lividus population sampled monthly near Alghero (Italy) from November 2004 to October 2005. Gonad index (GI) of the sea urchins was also evaluated. Statistical analyses showed significant differences of GI between 2 distinct periods of the year: late fall-winter and spring-late summer.
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Ecosystem effects of fishing in kelp forest communities
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Full-text available
  • Jun 2000
Kelp forests, highly diverse cold water communities organized around the primary productivity and physical structure provided by members of the Laminariales, support a variety of fisheries, and the kelp itself is harvested for alginates. Worldwide, these communities generally share susceptibility to destructive overgrazing by sea urchins. The impact of sea-urchin grazing is governed by the ratio between food availability and grazing pressure, thus factors affecting the abundance of both urchins and kelps are central to ecosystem integrity. Some kelp ecosystems share a second generality, the association of exploitation of various urchin predators with destructive levels of urchin grazing, leading to cascading implications for other species dependent on the productivity and habitat provided by the kelps. Competition between abalones and sea urchins also affects some kelp communities. These ecosystem-structuring processes are complicated by a variety of bottom-up and top-down factors, including variability in ocean climate affecting kelp productivity and recruitment of key species, and echinoid disease, potential ecosystem effects of fisheries for predators, abalones, sea urchins, and kelps are reviewed biogeographically. Given the hundreds to thousands of years that many nearshore marine ecosystems have been exploited, no-take marine reserves may be the only way to determine the true ecosystem effects of fishing. (C) 2000 International Council for the Exploration of the Sea.
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Implications of temporal and spatial variability in Paracentrotus lividus populations to the associated commercial fishery
Article
  • Dec 2001
Analysis of population structure and behaviour of a semi-enclosed and theoretically non-fished population of the echinoid Paracentrotus lividus at Lough Hyne marine nature reserve, Co. Cork, Ireland, showed distinct variability. Aspects of the behavioural variability in this species have significant consequences for the natural fishery harvest potential of this species. Whether or not, when and where individuals migrate to the upper surfaces of rocks varies on a local and regional scale as well as seasonally. The effect of this is apparent changes in (a) the population structure, (b) the population size and (c) the population centres of abundance. The population structure and size of the Lough Hyne population has changed substantially, as have those on a larger spatial scale, although the causative agents are debatable. Such changes are the result of large-scale mortality of adults and failure of cohort recruitment. Despite the undeniable pressures of overfishing at many localities, it seems likely there is a strong `natural' and possibly predictable element to the variability in P. lividus population size and structure. For the restoration and sustainable harvest of Irish P. lividus aspects of its behavioural ecology need to be taken more closely into consideration.
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Solutions to the ‘Tragedy of the Commons’: Sea-urchin Management in St Lucia, West Indies
Article
  • Jun 1991
  • ENVIRON CONSERV
Possible solutions to the commons problem have rarely been investigated systematically by the use of biological data on the status and sustainability of the resource. The edible White-spined Sea-urchin ( Tripneustes ventricosus ) resource of St Lucia, West Indies, is highly prized and vulnerable to exploitation, as is indicated by recent declines in its stocks. In the south-east of St Lucia the resource was almost entirely depleted in an area in which access was free and open. It was not depleted in the other two areas in which there were access controls. In one case, the area was under government control as a marine reserve; in the other, there was a locally practised ‘closed season’ and community-based management of access into a bay. The results of our study indicated that both government controls and informal, community-level controls can lead to successful resource-management outcomes. These findings challenge the ‘conventional wisdom’ that commonly-owned resources are destined to be overexploited.
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