Status of the American oyster Crassostrea virginica (Mollusca: Ostreidae) resource in Cauto river, Cuba

A. Betanzos-Vega1; J. M. Mazón-Suástegui2*; R. Puga Millán1; M. A. Avilés-Quevedo3; M. Formoso García1

1. Centro de Investigaciones Pesqueras (CIP). Calle 246 No. 503 entre 5ta. Avenida y Mar, reparto Barlovento, Municipio Playa. La Habana, Cuba, C. P. 19100., Centro de Investigaciones Pesqueras,

<state>La Habana</state>
, Cuba , 2. Centro de Investigaciones Biológicas del Noroeste, S.C. (CIBNOR). Av. Instituto Politécnico Nacional 195, Col. Playa Palo de Santa Rita Sur, La Paz, B.C.S. México. C. P. 23096., Centro de Investigaciones Biológicas del Noroeste, Centro de Investigaciones Biológicas del Noroeste, S.C.,
<city>La Paz</city>
<state>B.C.S.</state>
, Mexico ,
3. Investigador Independiente, Bahía Concepción 116, Fracc. Sudcalifornia, La Paz, Baja California Sur, México. C. P. 23080.,
<city>La Paz</city>
<state>Baja California Sur</state>
, México

Correspondence: *. Corresponding author: José Manuel Mazón-Suástegui, Centro de Investigaciones Biológicas del Noroeste, S.C. (CIBNOR). Av. Instituto Politécnico Nacional 195, Col. Playa Palo de Santa Rita Sur, C. P. 23096, La Paz, Baja California Sur, México. Phone: +52(612) 123 8417. E-mail.: E-mail:


Abstract:

The phenotypic identification of Crassostrea virginica, Gmelin (1791), as a natural resource in the Cauto River, Cuba, occurs in 2016. The species is part of the commercial catch in the southeastern region of Cuba since 2007. Fishing is free, without reproductive prohibition regulations and the same legal minimum catch size (40 mm) of mangrove oyster Crassostrea rhizophorae, Guilding (1828) is applied. The production of both species is not differentiated in the fisheries statistics of Cuba. This makes it difficult to evaluate and manage the entire oyster resource, so it was a first stock assessment and fishery production of C. virginica in the Cauto River. The annual total catch data 2010-2015 were obtained from fishing companies and population sampling and exploration was carried out, determining the total area of banks, the abundance of oysters in number and weight, and the mean population size. The population mean size decreased from 68.30 ± 18.22 mm in 2011 to 42.6 ± 11.70 mm in 2014, and abundance was significantly reduced in 2013 and 2014 compared to 2011 and 2012, with signs of exhaustion in the population, which needed a catching total banning. As a result of this administrative strategy, a population indicated a slight increase in abundance and size but did not reach levels of abundance for a maximum sustainable catch. Regulatory measures for the management of the C. virginica fishery in Cuba are proposed.

Received: 2017 August 14; Accepted: 2017 December 4

revbio. 2018 ; 5(1)
doi: 10.15741/revbio.05.2018.06

Keywords: Keywords: Fishery, bivalves, oysters, Caribbean islands.

Introduction

The Caribbean oyster or mangrove oyster Crassostrea rhizophorae (Guilding, 1828), was considered for a long time the only oyster native to the insular Caribbean (Jory and Iversen, 1985; Creswell, 2011). The oyster production in Cuba exceeded 3,000 t during the seventies, with contributions of aquaculture of up to 50 % (Frías and Rodríguez, 1991). Nevertheless, during the last decade, the national production has been lower than 1,500 t yearly and a fraction lower than 20 % comes from oyster farming. The mangrove oyster C. rhizophorae in Cuba shows a reduction in its abundance and growth in some natural zones, due to the river damming and reduction in the levels of primary productivity (Mazón-Suástegui et al., 2007).

Although American oyster Crassostrea virginica (Gmelin, 1791) had been reported towards the south central of Cuba, micro-located in a specific area of the Cienfuegos bay (Fernández-Milera and Argüelles, 1978), this species had not been part of the commercial catching. In 2007 natural oyster banks were discovered in subtidal habitat of the Cauto river, southeastern region of Cuba, and later, in 2012, in the basin of the river Cuyaguateje on the southwest of Cuba, although at a lower scale. The species discovered on the Cauto river was named by the fishermen “ostra de fondo” (bottom oyster), and recently identified phenotypically as American oyster C. virginica and registered as a natural resource in commercial use (Betanzos-Vega et al., 2016).

The American oyster (C. virginica) which is making subtidal natural banks in the Cauto river, presents the largest medium size, total weight and efficiency in meat (%) than the mangrove oyster (C. rhizophorae) which inhabits in an inter-tidal environment. Therefore, C. virginica is considered an emerging species for aquaculture in Cuba and the insular Caribbean (Betanzos-Vega et al., 2016). In Cuba, the fishing zones are assigned for their use to state companies, according to spatial planning (DRP/MIP, 1989), with permissible fees and specific closed seasons, according to the available fishing resources, and this includes the banks of natural mangrove oyster C. rhizophorae. The extraction of C. virginica in the Cauto river is performed with the participation of various fishing companies located in the southeast region of Cuba, with unrestricted access to that natural resource, due to the lack of regulations regarding specific spatial planning for American oyster.

Currently, the oyster catching is not distinguished by species in the national statistics of Cuba (ONEI, 2015), because the involved companies extract concurrently mangrove and bottom oyster, and register the catching as “oyster”, without further detail or specification. The plans or fees of annual catching are established in a general way for the resource “oyster”, without distinguishing a species from another, applying the minimum legal size (40 mm) established for the mangrove oyster C. rhizophorae (Resolution MINAL No. 126, 2009) issued by the direction of Science and Fishing Regulations of the Ministry of Food Industry of Cuba.

Since February 2014, a drastic decrease in oyster production of the Cauto river occurred. Applying a precautionary focus, the companies and authorities of the Fishing Regulations Direction agreed on a local catching moratorium specifically for C. virginica, from September 2014 to December 2016. The purpose of this work is to establish scientific basis for the rational exploitation of C. virginica, performing a first evaluation of the natural bank and the status of the resource in the Cauto river, and to propose measures for its protection and sustainable fishing management.

Materials and Methods

Field of study

The Cauto river is the largest of Cuba and its bed extends for 343 km, with a maximum width of 175 m towards its delta. It flows into the northeast of the southeastern platform of Cuba (20°32.922’N - 077°14.726’W), in the Gulf of Guacanayabo (Figure 1). Since 1967 the damming of this and other subordinate rivers has increased, decreasing from 50 to 70 % the contribution of sweet water to the coastal area (Baisre and Arboleya, 2006). This has produced a progressive increase of salinity, incorporating marine and salty characteristics in the zones of the Cauto river beyond 30 km from its estuary; spreading the mangrove and American oyster banks by effects of salinity (Betanzos-Vega et al., 2016). The spreading of C. virginica occurs intermittently in nine sites, from the area known as El Desvío (20°34.357’N - 077°08.283’W) up to the zone of La Punta (20°37.824’N - 077°02.515’W) (Betanzos-Vega et al., 2016) (Figure 1).


[Figure ID: f1] Figure 1.

Study area where the natural bank of C. virginica is located in the Cauto river, fragmented into nine enumerated zones, framed in black circles and with the name of each locality the four selected zones for annual monitoring purposes.


Extraction process

For the analysis of the extraction process of C. virginica in the Cauto river, fishing zones and facilities of the companies located in the ports of Gulf of Guacayanabo: Manzanillo and Niquero (Granma province), and Guayabal (Las Tunas) were visited. The oyster activity on the basin of Cauto (ríver and adjacent lagoons), is directed to the mangrove oyster and is land responsibility of the fishing company of Manzanillo, with unrestricted access to “bottom oyster”. Only this company has a record of the unloading of each species since 2010. To determine the catching of this species by the other companies, it was necessary to analyze the monthly operation data by each ship and fishing zones. Finally, the catching of C. virginica was registered according to the volume of oyster in the Shell, delivered by all the ships that operated in the zone of the Cauto river during the term of 2010-2015.

To evaluate the fishing it was not possible to obtain specific information about fishing effort (days/fishing) and other fishing variables, due to the differences between companies about their records of fishermen per ship and effective time of fishing, considering different navigated distances from their base to the fishing zones and back to dock with the product. The relative data to fishing turned out insufficient to apply traditional models of fishing evaluation. For this reason, to determine the current state of the resource C. virginica of the Cauto river, some points of population reference were used (Smith et al., 1993; Cadima, 2003), obtained from samples made in November 2011, 2012, 2014 and in December 2013 and 2016; months in which the goals or catching fees for the next year are planned.

Population parameters

For the study of the population parameters, in November 2011, a research in the Cauto river was made from the access canal (Desvío), until the “La Punta” zone (18 km) (Figure 1), covering a total area of 0.360 km2. Explorations were made on both edges of the river, on a parallel border to each edge (0.50 m average depth), until the border of the river’s drop-off (average depth of 2.3 m), at an average distance (width) of 10 m from each littoral. Nine sites with conglomerations of C. virginica were counted (Figure 1). Based on the experiences and criteria of oyster fishermen and local shore population, it was known that, due to the extension and fragmentation of the bank, there are exploitation and low exploitation zones, and it was considered that both could offer different information but complementary about this resource. Applying this criterion, four zones with oyster banks were chosen (Figure 1) meaningful to carry on an annual monitoring: El Júcaro (zone 1) and Manajuana (zone 3), which are being exploited, Cabezada (zone 5) and Guasimilla (zone 8) which register very little extraction activity.

To know the total dimension of the ship, supported by a GPS Garmin 48 of 12 channels and the software MapInfo version 8, the area (km2) of each of the nine zones with C. virginica presence was determined (Figure 1, Table 1). The total area of the natural bank was estimated in 0.145 km2.

Table 1.

Geographical localization of the center each oyster zone of C. virginica, including area of bank (km2) and distance (nautical miles) between sites.


Zone Geographical position Area (km 2) Distance (nm)
1 20°35.211’N 077°06.405’W 0.022 -
2 20°35.640’N 077°05.533’W 0.006 0.976
3 20°35.650’N 077°04.688’W 0.006 0.831
4 20°35.578’N 077°03.800’W 0.022 0.970
5 20°36.437’N 077°03.943’W 0.019 1.022
6 20°36.417’N 077°03.408’W 0.016 0.588
7 20°36.207’N 077°02.995’W 0.010 0.798
8 20°37.195’N 077°02.916’W 0.024 1.107
9 20°37.824’N 077°02.515’W 0.021 0.745

The abundance of C. virginica was determined using the sampling method based on quadrants (Weinberg, 1981; Solano, 1995). To determine the number of oysters/m2 (N/m2), a square iron frame (1 m2) was used, it was randomly thrown five times over the oyster bank to manually collect through free diving, all the organisms located within the delimited area. The living oysters of each sample were cleaned, measured, weighed and counted. To estimate the weight of oysters/m2 (kg/m2), the Polder analogic scale was used, with a range of 0 to 10 kg and a precision of 25 g. With this data the abundance in number and weight (N/m2 y kg/m2) of each replica was determined, from each evaluated zone, and the total abundance of the bank; making the necessary conversions to obtain the total abundance in Kg/km2 (production per area).

From the production per area or density (D) in weight (kg/Km2) estimated for the entire bank and from the total bank area (A) in Km2, the total population biomass (B) was estimated in metric tons (t), following the equation B = A*D (Cadima, 2003).

With the capturing data (C) and biomass (B) of the term 2010 - 2014, the relation between both variables was examined with the purpose of evaluating the status of the resource C. virginica in the Cauto river. A dome-shaped scatter graph was obtained, very similar to the typical relation between both variables according to the Schaefer production model (1954) . Facing the impossibility to adjust a model because of the short extension of the series of data, a second-degree polynomial equation with intercept in the origin was estimated, this equation has the same shape as in Schaefer model, such equation is as follows:

C = -0.0007*B2 + 1.0699*B

To determine the reference points for the fishing management, the equation was evaluated for determined values until the maximum catching and its corresponding biomass, as well as the maximum biomass in absence of extraction activity, which allows to obtain estimates of:

MSC: Maximum sustainable catching
BMSC: Biomass for the MSC
B0: Biomass in no exploitation status

Through the relation F = C/B (where F: fatality rate per fishing) the F for each year and the FMSC = MSC/BMSC, with the aim of making balance curves of B and C regarding F determined values and comparing the results of the fishing with the estimated reference points. Particularly in the case of year 2010, with a registered catching of 298 t, but without determining biomass, the previously described relations were used, to estimate the values of B and F which theoretically and according to the tendency in the available data, corresponded to that year.

The minimum population biomass spawning level required, to insure the sustainability of the wild population of C. virginica in the Cauto river, was estimated according to the analysis of the Minimum Biological Acceptable Level (Cadima, 2003), considering the 30 % of the average biomass of the population bigger in size than the first maturation size (40 mm) (Garrido et al., 2007).

For the biometry, the shells of the living oysters from each sample were measured in their total length (Lt, mm) on the dorsal side, from the umbo until the furthest opposite border of the shell, with a vernier of 0.05 mm precision. In all the evaluated years, the mean size and total size per bank zone was determined; and the total mean abundance composition of the bank, considering size intervals. 4 intervals or classes were established: from 0 to 20 mm (recruits), from 20 to 40 mm (young and pre-adults), from 40 to 60 mm (adults in reproduction age) (Rodríguez-de La Cruz, 1988; Galtsoff, 1964), and bigger than 60 mm. This last class includes oysters in plain reproduction capacity and which may have spawned more than once (Garrido et al., 2007).

Statistical Analysis

Before analyzing the data, its normality (Kolmogorov-Smirnov) and homogeneity in its distribution (Bartlett) were confirmed (Zar, 1984). The size (mm) and abundance (number of oysters/m2 and kg/m2) were compared, among the four selected sites and sampled years, through a single factor ANOVA, and from observation, to determine which measurements had been significantly different, the multiple comparisons test of LSD (Less Significant Difference) of Fisher was used. All the tests were made with a level of p<0.05.

Results and Discussion

During the observed years in the Cauto river, most of the C. virginica oyster production was reported from 2010 - 2013, with a mean annual catching of 379 ± 133.4 t and contributed with almost 30 % to the national oyster catching, (1,271 t) (ONEI, 2015). This shows the importance of this species and the oyster bank in the Cauto river. From the global C. virginica catching from the Cauto river, estimated for the 2010 - 2015 period, the fishing company of Manzanillo extracted 80.1 %, the fishing company of Guayabal 13.7 % and Niquero 6.2 %. According to the annual variation of the total C. virginica catching in the Cauto river, during the 2010 - 2013 period, a stability with a mean of 320 ± 35.7 t was maintained. After the 2013 catching (556 t), a clear and drastic trend to reduction was observed (Figure 2), which made a catching banning agreement necessary specifically for C. virginica, from 2014 to 2016.


[Figure ID: f2] Figure 2.

Annual variation of the total catch (t) of C. virginica oyster in the Cauto river, Cuba.


During 2011 and 2012 a density higher than 200 oysters/m2 was registered in all the evaluated zones (Table 2), and this value has been suggested as an acceptable minimum abundance index in a natural population, to guarantee a sustainable fishing of C. virginica (Palacios-Fest et al., 1988). However, since 2013 a significant reduction in abundance was observed (N/m2 y kg/m2) and oyster mean size, by zones and in total, registering in general values lower than 200 oysters/m2, with a minimum of 50 oysters/m2 in 2014 (Table 2). In December 2016, having passed two years since the catching banning for C. virginica of the Cauto river, an increase in its abundance was registered (101 oysters/m2) and in the mean size of the population, compared to 2013 y 2014 (Table 2). Despite this recovery, neither the production levels nor the population indexes registered during 2011 and 2012 were achieved. In general terms, the total minimum abundance of the C. virginica population, registered from November 2011 to November 2014 dropped significantly to 17.36 %.

Table 2.

Annual mean values of length (mm), mean abundance (number of oysters/m2 and kg/m2) by evaluated zones, and total mean ± standard error (SE) of C. virginica population in the Cauto river, Cuba.


Nov-2011 El Júcaro Manajuana Cabezada Guasimilla Total mean ± SE
Mean size (mm) 60.6a 61. 2a 76.5b 74.8b 68.3 6.21
Oysters/m2 253a 279b 315c 306c 288 5.76
kg/m2 7.8a 7.6a 9.3b 9.1b 8.4 0.19
Nov-2012
Mean size (mm) 51.7a 64.2b 68.5b 67.7b 63.0 4.76
Oysters/m2 232a 244a 309b 286b 268 8.39
kg/m2 7.6a 6.8b 9.3c 8.8c 8.1 0.26
Dic-2013
Mean size (mm) 39.8a 42.2a 48.4b 51.2b 45.4 2.15
Oysters/m2 136a 122a 168b 175b 150 6.90
kg/m2 5.1a 4.9a 5.5b 5.7b 5.3 0.13
Nov-2014
Mean size (mm) 40.9a 41.3a 44.2b 43.8b 42.6 1.68
Oysters/m2 72a 47b 45b 34c 50 4.33
kg/m2 3.7a 2.8b 2.7b 2.1c 2.8 0.17
Dic-2016
Mean size (mm) 47.3a 46.6a 46.9a 48.0a 47.2 1.75
Oysters/m2 88a 92a 109b 115b 101 3.97
kg/m2 ND ND ND ND ND ND
abc.

TFN1 unequal letters in the same row, indicate significant statistical difference (Fisher’s LSD), p<0.05. ND = not determined.


A similar research in the Mecoacán Lagoon (state of Tabasco, México), revealed for wild C. virginica (Garrido et al., 2007); a reduction of 64 % mean abundance (140 oysters/m2), compared to the reported by Solano (1995), of 394 oysters/m2 at the beginning of 1980, and they blame this reduction to a fishing deficient administration, due to not applying precautionary management criteria (FAO, 1997), more than bio-ecological issues.

The mean comparison table (Figure 3), shows that there were no significant differences in the amount of oysters/m2 of class 0 - 20 mm (recruits), 20 - 40 mm (young and pre-adults) y 40 - 60 mm (adults), within 2011 and 2012. On the other hand, during 2013, 2014 and 2016, the abundance (oysters/m2) dropped in size in all the classes, and showed significant differences compared to the 2011 - 2012 term. This indicates an affectation not only in the size of the catching (> 40 mm) but also in all the population. Even in 2016, after two years of official catching moratorium, although an increase in oyster/m2 abundance in all the size intervals was observed, this recovery did not show significant difference compared to 2014.


[Figure ID: f3] Figure 3.

Mean annual abundance (oysters/m2) and size intervals (mm) of the C. virginica oyster natural banks evaluated in the Cauto river, Cuba. The vertical lines show the confidence interval according to Fisher’s LSD. Unequal letters in the same size interval, indicate significant statistical difference (p<0.05).


Considering that the mean size of first maturation of C. virginica is 40 mm (Galtsoff, 1964; Sevilla and Mondragón, 1965), the minimum catching size of 40 mm stablished for Cuba (Resolution MINAL No. 126, 2009) for the mangrove oyster (C. rhizophorae), which is sexually mature from sizes smaller than 30 mm (Nikolic y Soroa-Boffill, 1971; Lenz y Boehs, 2010), cannot be applied. Therefore, applying this criterion for C. virginica would have a negative incidence over the spawn stock and the recruitment of the species, putting its fishing sustainability at risk.

Taking into consideration the commercial size (≥ 60, ≥ 70 y ≥ 80 mm) applied for C. virginica in the Mexican states of the Gulf of Mexico and in nations of the Central American Caribbean (Palacios-Fest et al., 1988; Lodeiros and Freites-Valbuena, 2008; SAGARPA, 2012), in this research the oysters with a size greater than 60 mm, corresponding to adults in full reproductive capacity, are proposed as fishable fraction. This criterion should be considered as a precautionary proposal of the commercial size specific for C. virginica in Cuba.

In 2013 and 2014, the total biomass of C. virginica in the Cauto river and the adult biomass, reduced significantly compared to 2011 and 2012 (Table 3). This was in agreement with the annual reduction in the total oyster/m2 abundance (Table 2), observing that in 2011 and 2012, years of greater abundance (> 200 oysters/m2), the biomass with commercial catching size (≥ 60 mm) represented ~ 40 % of the total biomass. This confirms that an additional condition to achieve a sustainable catching, is that the fishing should be accomplished in the natural banks with more than 200 oysters/m2 (Palacios-Fest et al., 1988), and that they show more than 40 % of oysters with a size ≥ 60 mm.

Table 3.

Estimated annual biomass (t) of Crassostrea virginica in Cauto river, Cuba.


Variables nov-2011 nov-2012 dic-2013 nov-2014
Pre-adult biomass (< 40 mm) 501.8 492.7 424.2 182.3
Adult Biomass (> 40 mm) 726.6 591.1 262.4 95
Total biomass 1228.4 1083.8 686.6 277.3
Potential commercial size biomass (> 60 mm) 565.1 426.6 171.4 30.9

The minimum biological acceptable level (MBAL) of oysters (30 %) with reproduction capacity to guarantee the fishing sustainability (Cadima, 2003), was estimated from the adult biomass (> 40 mm) of the 2011 - 2013 term, without including the adult biomass of 2014, due to the extension since September of the same year. The MBAL value obtained was 300 t; however, the total biomass of the adult population in December 2013 (262.4 t) and November (95 t) (Table 3), were lower than the reference (300 t). Below that adult biomass level, the recruitments would be lower than the average, with the subsequent affectation to the population and the fishing (Smith et al., 1993; Cadima, 2003; Garrido et al., 2007).

The adjusted function as of the total catching-biomass analysis observed (Figure 4); allowed to have the theoretical balance curves of C and B in function of F respectively, and the observed values (Figures 5 and 6).


[Figure ID: f4] Figure 4.

Relationship observed between yield and biomass during 2011-2014 and theoretical curve fitted with r2 = 0.56. The unexploited biomass (B0) and the points of reference of maximum sustainable yield (MSY) and the corresponding biomass (BMSY) are represented.



[Figure ID: f5] Figure 5.

Yield equilibrium curve based on the fishing mortality rate (F) and values observed during 2010-2014. Maximum Sustainable Yield (MSY) benchmarks and the corresponding fishing mortality rate (FMSY).



[Figure ID: f6] Figure 6.

Biomass balance curve based on the fishing mortality rate (F ) and values observed during 2010-2014. The unexploited biomass (B0) and the biomass reference points for the maximum sustainable yield (BMSY) are represented and the corresponding fishing mortality rate (FMSY).


The quantified results of this reference points were:

B0 = 1528 t, MSC = 409 t, BMSC = 764 t and FMSC = 0.54

According to the outcomes of this analysis, to avoid overfishing and natural resource exhaustion, a reasonable catching would be 80 % of MSC (Hilborn y Stokes, 2010), which in this case is 327 t. This indicates that at the beginning, the fishing kept at a sustainable status by obtaining an annual mean catching of 320 t during the 2010 and 2012 term, but due to the catching magnitude during 2013, an overfishing took place when F2013 was 51 % higher than FMSC. Therefore, the biomass in December 2013 and during the first semester of 2014, reduced below BMSC 10 % and 64 % respectively, which describes the resource as ran out in 2014, and it is corroborated in the reduction of F observed.

Like the sustainable management of the fishing, it is necessary to implement, in a short term, the handmade cultivation of the American oyster C. virginica beginning with the natural seed. In the medium or long term, developing the technical cultivation in hatcheries, which guarantees not only a sustainable increase of the oyster production in Cuba, but also the possibility to obtain individual seed of C. virginica bound for repopulation, and a way to export quality seed to countries of the Caribbean region (Mazón-Suástegui et al., 2009; Creswell, 2011).

As a result of the present research, the following recommendations are made:

Maintaining a recurring monitoring of the C. virginica natural resource status and defining the gonadic and spawning maximum maturation periods and population massive spawning, to implement para temporary banning.

Defining the extraction activity of C. virginica in Cuba, as an independent fishing of the C. rhizophorae fishing, differentiating the information in the fishing statistics of the country.

Applying a minimum legal size of 60 mm for C. virginica in Cuba, performing extraction with commercial purposes only in the natural banks with an abundance greater than 200 oysters/m2; carrying on, precautionarily, a catching no greater than 50 % of the extractible population biomass (Lt ≥ 60 mm), unless the necessary biological-fishing studies for an adequate fishing management of the resource are performed.

Conclusions

The production of the American Oyster in Cuba comes from a recent fishing, and the results of this research indicate population depletion due to overfishing, therefore, if a precautionary focus or implementing measures for a sustainable management are not applied, C. virginica could disappear as a commercial resource.

The application of the catching moratorium from 2014 to 2016, prevented a greater affectation to the population of this resource in the Cauto river, but not enough such as to stablish the population abundance to the original or higher productivity levels.

Additional causes to overfishing considered are: 1) the inexistence of banning regulations to protect the maximum spawning and population recruiting periods; 2) the incorrect application of C. rhizophorae commercial size (≥40 mm) for the C. virginica commercial catching; 3) the lack of application of a differentiated catching fee for this species; and 4) the C. virginica free-access extraction policy in the Cauto river.


Acknowledgements

The authors thank the technical personnel and oyster fishermen of the fishing companies of Manzanillo, Niquero and Guayabal, Cuba. It is also appreciated the support of the projects SEP-CONACYT-CB 258282 AND PROINNOVA-CONACYT/PEASA 241777, connected with CIBNOR, Mexico.

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