Assessing the suitability of the minimum capture size and protection regimes in the gooseneck barnacle shellfishery (original) (raw)
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Estimating a new suitable catch size for two clam species: Implications for shellfishery management
The present study analyzes the weight gain patterns per unit of size and estimates the minimum suitable catch size of two clam species: the carpet shell clam Ruditapes decussatus and the Manila clam Ruditapes philippinarum. For this purpose, data from the two largest estuaries along the northern coast of Spain (Cantabrian Sea) were used. The lengtheweight relationship of both studied species was estimated using two models: a classic allometric model and a nonparametric regression model based on local linear kernel smoothers. Additionally, first derivatives were used to estimate a minimum capture size for this species, corresponding to the size at which the first derivative reached the maximum. Within this context, the models application showed (a) the nonparametric model resulted in a better fit of data for both species (b) different minimum catch sizes for each species based on maximum length (49.5 mm for R. decussatus and 44.7 mm for R. philippinarum), both considerably larger than the currently established in EU and (c) an effect of estuaries and zones on individuals weight gain patterns. This confirmed the nonparametric model as an alternative approach to analyze the lengtheweight relationship for the studied species and to estimate a minimum suitable catch size of capture. The application of the specific catch sizes obtained in this study could lead to an increase in available commercial stocks of both species and positive effects on the conservation of the native species. In addition, the estimated zone-specific weight-gain patterns and minimum catch sizes could support a zone-based management. Therefore, this study provides a preliminary study and a starting point to consider the revision of the minimum legal size of the studied species in order to improve the current shellfishery management model.
Scientia Marina, 2011
The stalked barnacle Pollicipes pollicipes (Gmelin, 1790) is an important shellfish resource in Portugal. Due to the social-economic importance of barnacle harvesting, a management plan aimed at achieving a controlled and sustainable activity (including temporal and spatial closures, rotational harvesting, a limited number of harvesting licenses, bag and size limits for catches and catch reporting) was implemented in 2000 at the Berlengas Nature Reserve (RNB) in central Portugal. We evaluated the bag and size limits imposed by the management plan, performing observations on harvesting activity and asking licensed harvesters and RNB staff about these measures. Both inquiries and observations suggest that licensed harvesters are not following the bag and size limits imposed. Mean amounts captured in RNB varied from 14 to 24 kg per harvester/day, but 25% of the observations corresponded to higher catches per individual than the total amount allowed (20 kg). Only half of the sampled amounts (taken in autumn 2005 and 2006) were in agreement with the size limit regulation and 50% of the total biomass comprised individuals of maximal rostro-carinal length (RC) ≥25 mm. For most harvesters, size limit is the most difficult management rule to fulfil. Both harvesters and RNB staff agree that surveillance is scarce and is a major problem of this fishing activity. In order to achieve a more sustainable use of this resource, we propose the implementation of a more effective surveillance and monitoring plan, the definition of a unique landing site, the maintenance of the bag limit (20 kg) and a reduction of the size limit (50% of total biomass comprising individuals ≥22 mm RC).
Scientia Marina, 2011
The stalked barnacle Pollicipes pollicipes (Gmelin, 1790) is an important shellfish resource in Portugal. Due to the social-economic importance of barnacle harvesting, a management plan aimed at achieving a controlled and sustainable activity (including temporal and spatial closures, rotational harvesting, a limited number of harvesting licenses, bag and size limits for catches and catch reporting) was implemented in 2000 at the Berlengas Nature Reserve (RNB) in central Portugal. We evaluated the bag and size limits imposed by the management plan, performing observations on harvesting activity and asking licensed harvesters and RNB staff about these measures. Both inquiries and observations suggest that licensed harvesters are not following the bag and size limits imposed. Mean amounts captured in RNB varied from 14 to 24 kg per harvester/day, but 25% of the observations corresponded to higher catches per individual than the total amount allowed (20 kg). Only half of the sampled amounts (taken in autumn 2005 and 2006) were in agreement with the size limit regulation and 50% of the total biomass comprised individuals of maximal rostro-carinal length (RC) ≥25 mm. For most harvesters, size limit is the most difficult management rule to fulfil. Both harvesters and RNB staff agree that surveillance is scarce and is a major problem of this fishing activity. In order to achieve a more sustainable use of this resource, we propose the implementation of a more effective surveillance and monitoring plan, the definition of a unique landing site, the maintenance of the bag limit (20 kg) and a reduction of the size limit (50% of total biomass comprising individuals ≥22 mm RC).
Development of a Sustainable Gooseneck Barnacle Fishery; Initial Investigations
2017
In Spain, gooseneck barnacles, “percebes,” are an overfished delicacy fetching a high market price ($50/lb). Oregon fishing communities show interest in developing a percebes market utilizing Pollicipes polymerus. We aim to inform resource managers to avoid over harvesting Oregon goosenecks. In summer 2016, we investigated the current status of P. polymerus populations with three primary objectives: A. Describe Oregon gooseneck populations on coastal jetties to inform harvest management. B. Explore possible mariculture development for onshore gooseneck production. C. Establish a collaborative multistakeholder framework for sustainable fishery development. We surveyed eight southern Oregon jetties using transect sampling and photographic documentation of gooseneck populations, which we characterized by size-frequency distribution and density. We observed spatially explicit trends according to tidal height and large variability in populations between jetties. We estimate there to be r...
ICES Journal of Marine Science, 2012
Parada, J. M., Outeiral, R., Iglesias, E., and Molares, J. 2012. Assessment of goose barnacle (Pollicipes pollicipes Gmelin, 1789) stocks in management plans: design of a sampling program based on the harvesters' experience. – ICES Journal of Marine Science, 69: 1840–1849. Management plans of coastal marine resources require a wealth of information on socioeconomic topics, harvesting activities, population dynamics, and stock status. Moreover, the information provided by technical experts must take into account the needs of the managers. It must also adapt to schedules to serve a useful purpose. In many cases, the methodologies used by research teams are not directly applicable as they may be too complicated, aimed at specific objectives related to basic scientific work, or too costly to apply to long-term monitoring of extensive shellfish beds. Also, rocky coastlines exposed to heavy wave action preclude the use of sampling techniques that involve time-consuming data collection...
Journal of Shellfish Research
The gooseneck barnacle Pollicipes pollicipes is a very valuable marine resource on the coasts of Spain and Portugal. To maintain the sustainable exploitation of this species, periodical large-scale population assessments are essential. Because of the heterogeneous distribution of these populations in aggregates, together with the difficulties associated with sampling (i.e., access to rocky reefs, wave exposure, high tides, etc.), there is a lack of studies in this regard. In light of these constraints, the coverage, biomass, and available stock of gooseneck barnacle were first estimated using a novel semiquantitative method along a 215-km long coast at 10 fishing zones and three tidal levels. This study contributed to the first assessment of the distribution variability of gooseneck barnacle in the Cantabria region (N Spain), as the first step toward a long-term monitoring goal. The proposed method is based on a general coverage (GC) estimation, by means of (1) quantitative coverage measurements on quadrats (50 cm 3 50 cm) located along vertical transects covering the intertidal bandwidth and corrected by tidal level bandwidths, (2) semiquantitative coverage estimates in larger areas, including 5 m on either side of the quadrats along the transect. Biomass samples were collected at each sampling point by scraping the 50 cm 3 50 cm quadrat and fresh weight of the samples was measured. This method arrives at the biomass estimates by means of a power regression model for the coverage-biomass relationship. The population distribution pattern along the coast was also explored separately, by commonly used (1) quantitative coverage estimates in quadrats with no bandwidth correction (sample coverage, SC) and (2) semiquantitative estimates, as in the proposed method (transect coverage, TC), both of which included biomass sampling. Biomass and standing stocks values obtained using GC were lower and consumed less sampling time than those obtained by TC, and particularly SC. The results suggest that the proposed method might be suitable for the assessment of P. pollicipes populations in large coastal areas, as it potentially avoids stock overestimation by detecting the spatial distribution heterogeneity and reduces the sampling time.
Simulation Modeling to Explore the Effects of Length-Based Harvest Regulations forIctalurusFisheries
North American Journal of Fisheries Management, 2016
Management of Blue Catfish Ictalurus furcatus and Channel Catfish I. punctatus for trophy production has recently become more common. Typically, trophy management is attempted with length-based regulations that allow for the moderate harvest of small fish but restrict the harvest of larger fish. However, the specific regulations used vary considerably across populations, and no modeling efforts have evaluated their effectiveness. We used simulation modeling to compare total yield, trophy biomass (B trophy), and sustainability (spawning potential ratio [SPR] > 0.30) of Blue Catfish and Channel Catfish populations under three scenarios: (1) current regulation (typically a length-based trophy regulation), (2) the best-performing minimum length regulation (MLR best), and (3) the best-performing length-based trophy catfish regulation (LTR best ; "best performing" was defined as the regulation that maximized yield, B trophy , and sustainability). The B trophy produced did not differ among the three scenarios. For each fishery, the MLR best and LTR best produced greater yield (>22% more) than the current regulation and maintained sustainability at higher finite exploitation rates (>0.30) than the current regulation. The MLR best and LTR best produced similar yields and SPRs for Channel Catfish and similar yields for Blue Catfish; however, the MLR best for Blue Catfish produced more resilient fisheries (higher SPR) than the LTR best. Overall, the variation in yield, B trophy , and SPR among populations was greater than the variation among regulations applied to any given population, suggesting that population-specific regulations may be preferable to regulations applied to geographic regions. We conclude that LTRs are useful for improving catfish yield and maintaining sustainability without overly restricting harvest but are not effective at increasing the B trophy of catfish. Catfishes (Family Ictaluridae) constitute one of the most important groups of freshwater fishes in North America (Irwin et al. 1999; Michaletz and Travnichek 2011). State agency opinion surveys often reveal that catfish are the third most sought-after sport fish group (Michaletz and Dillard 1999; Stewart et al. 2012); the Blue Catfish Ictalurus furcatus and Channel Catfish I. punctatus are particularly valuable commercially, recreationally, and economically (Irwin et al. 1999; Michaletz and Dillard 1999; Stewart et al. 2012). Recently, management efforts in many ictalurid fisheries have focused on producing trophy-recreational fisheries, especially for Blue Catfish (Kuklinski and Patterson 2011; Stewart et al. 2012).
Ecological Indicators, 2021
Body size plays a key role for the productivity and resilience of marine populations. This work analyses the variation in body size indicators taken from ~ 400 000 individuals during the period 2000-2018 for a set of 20 key commercial species of the small-scale fishery of Galicia (SW Europe). Mean body size showed relatively stable inter-annual trends during the study period, and, at the year level, mean body size for most species followed seasonal cycles. Body size was negatively related to the number of individuals caught per haul. Bathymetry also explained part of the variation in individual body size with species-specific depth affinities. Common trends in the species' body size showed an increasing trend in the northern region while decreasing in the south suggesting differences in local environmental conditions and/or in the dynamics of the fishery. The skewness of body size distributions varied slightly from year to year, although some species showed significant trends. The annual trend of the species-specific skewness was negatively related to the proportion of immature individuals in the catch and positively related to the rate of change in abundance, suggesting a reduction of recruitment success in response to differences in size-selective exploitation patterns probably ascribed to minimum landing size being generally below size at maturity. The combination of body size and abundance indicators revealed a relatively stable performance of some of the most important resources targeted by the Galician smallscale fishery sector during the last two decades. However, our study highlights also the need to align management measures with biological reference points in order to prevent long-term reductions in stock productivity.