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Maturity Assessment for the Implementation of the First Fishery Regulation in Patagonian Marine Gastropods
Abstract
In order to establish management measures for a new resource, the size at first maturity should be studied. This measurement is a powerful tool in enabling the sustainable exploitation of marine benthic resources. Patagonian marine gastropods are captured as complementary catches during scallop fisheries. Studies related to the size at first maturity were performed for edible marine gastropods in northern Patagonia and have been used for the creation of the first regulation of gastropod catches made by the Secretary of Fisheries of Chubut Province. The minimum capture size of some of the species included in this regulation was established from preliminary studies but needed histological confirmation. The present study aims to provide accurate information on the size at maturity by an assessment that includes first gonadal maturity and population size/weight data of Buccinanops deformis and Trophon geversianus, two edible species of marine gastropods with high abundance along the Patagonian Atlantic coast and elevated nutritional values in their edible tissues. By histological methods, females of B. deformis reach maturity at 2.8 cm and males at 1.95 cm. While by an alternative histological method (inflexion point method), females reach maturity at 2.76 cm and males at 2.1 cm. For T. geversianus, females reach maturity at 3 cm (inflexion point = 2.38 cm) and males at 1.65 cm (inflexion point = 2.01 cm). The maturity assessment of B. deformis and T. geversianus revealed that males reach maturity at a smaller size than females, probably due to the fact that females require a more gradual process in maturation with a greater reproductive investment. The size at first sexual maturity provides valuable information for establishing the minimum catchable size. Therefore, we estimate a minimum size limit for B. deformis of 3.6 cm and 3.5 cm for T. geversianus and suggest that fishery measurements for these species should be established by performing a particular maturity assessment in each fishery zone.
... Buccinanops cochlidium, commonly found in the subtidal zone in northern Patagonia, is distributed from Rio Grande do Sul (32 • S, Brazil) to Nuevo Gulf, Puerto Madryn (42 • S, Argentina) (Pastorino and Simone, 2021). These species are abundant throughout their distribution on the Southeast Atlantic coast and are valuable for the development of fisheries in the region (Cumplido, 2016;Cumplido et al., 2020;Bigatti et al., 2017). ...
... Nevertheless, B. deforme has been commercialized by artisanal fishermen in San Matías Gulf (Northern Patagonia) since 2000 (Narvarte, 2006), while other species are locally exploited and commercialized (Ciocco, 1995;Orensanz et al., 2006;Bigatti and Ciocco, 2008). Likewise, other edible species of the Patagonian Atlantic coast, such as Trophon geversianus and Tegula patagonica are considered as potential targets for consumption and massive commercialization (Bigatti et al., 2015;Cumplido and Bigatti, 2020), although they are not consumed locally. ...
... In the SJG, emphasis has been made that any commercial gastropod fishing is to be done manually, being selective (Bigatti and Ciocco, 2008). The size at reproductive maturity should be considered when establishing size limits, and is based in the size at which the females reach maturity Boman et al., 2018;Cumplido and Bigatti, 2020;Giménez and Penchaszadeh, 2003;Riestra et al., 2000;Wilcox et al., 2021;Zabala et al., 2013). This regulatory measure (Regulation 199/18) was the first established in Chubut Province and Argentina. ...
Marine gastropods are key items in small-scale fisheries worldwide, generating employment and high economic value in international markets. In North Patagonian Gulfs (Southwestern Atlantic), gastropods are landed as by-catch in bivalve artisanal fisheries, and thus no official statistics are reported. Recently, the first regulation of marine gastropod catches was established based on size at maturity for some edible species. However, additional biological-fishery data are necessary for developing a management plan if a regulated small-scale fishery is to be established. We provide the first preliminary estimation of the harvestable stock and other basic biological parameters of gastropods in the San José Gulf (SJG), a Natural Protected Area in Northern Patagonia. Density assessments are usually carried out using dredges or trawl nets that damage marine substrata, and thus we used data from non-destructive, drifting underwater visual census in transects, integrated with a Geographic Information System. We estimated the biomass, density, CPUE and the harvestable stock of Odontocymbiola magellanica and Buccinanops cochlidium, the main species currently landed in SJG. Visual surveys were conducted in 85,000 m², where both species were present in depths ranging from 5 to 20 m depth. For O. magellanica, the maximum densities were 0.02–0.04 individuals m⁻² with maximum CPUE of 12.8 kg diver⁻¹ 15 min⁻¹ and estimated harvestable biomass of 837.05 kg (S.D. = 189.96), whereas for B. cochlidium densities were 0.32–0.60 individuals m⁻² with maximum CPUE of 9.25 kg diver⁻¹ 15 min⁻¹ and 365.12 kg (S.D. = 81.86) of harvestable biomass. The delayed maturity and reproductive strategies of both species, among other biological parameters, require a precautionary approach. The total exploitable biomass estimated in our work clearly highlights the need for a very selective, small-scale fishery, operating under a well enforced management plan regulating their capture to ensure its sustainability in a Natural Protected Area.
... The Florida Horse Conch, Triplofusus giganteus (Kiener, 1840) [1], which is found from North Carolina to Yucatán, Mexico, can reach shell lengths over 600 mm, making it one of the a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 jump"), which coincide with the onset of gametogenesis [23,24]. The exact mechanism by which this happens is unknown, but many gastropod species exhibit a sharp increase in body mass at the onset of maturity [25] that could indirectly affect δ 13 C shell through changes in sizeor growth rate-related physiology or diet, independent of gamete production. Here, we use trends in δ 13 C shell in T. giganteus shells and additional supporting evidence from shell lengths of photographed spawning females in the wild to propose a hypothesis for age at first reproductive maturation. ...
The Florida Horse Conch, Triplofusus giganteus, one of the largest marine gastropods in the world, has been intensely exploited by shell collectors, curio dealers, and commercial harvest for over a century and is now in decline. Effective management of horse conch populations requires better data on commercial and recreational harvest intensities but also on the species’ intrinsic capacity to recover. Here, we use stable oxygen and carbon isotope sclerochronology to investigate the horse conch’s life history, including its maximum life span, growth rates, age at first spawning, and number of lifetime spawning seasons. The largest two shells studied (460 and 475 mm linear shell length) grew for 13 and 11 years, respectively. Growth curves for these shells, extrapolated out to the length of the record size shell (606 mm linear shell length) predict a maximum age of just 16 years. Carbon isotopes and field photographs of spawning females suggest that females mature relatively late in life. However, the largest horse conchs remaining in the wild are also smaller and younger than those studied here. Thus, the largest females left in the wild could have few lifetime spawning events. High fecundity can buffer horse conchs from overfishing but only if females reach spawning age and reproductive-age females are protected. Our study highlights the usefulness of stable isotope sclerochronology for characterizing the life histories of molluscan species now too uncommon to study through traditional mark and recapture approaches.
New marine mollusc fishery resources are constantly being incorporated to the international market. The marine gastropod Buccinanops cochlidium (Dillwyn, 1817) is a potential fisheries resource with excellent nutritional qualities. Recently, the first legislation that regulates marine gastropod fisheries based on size limits and reproductive seasonality was established in Argentina, although some biological parameters that are useful to its implementation are still needed. Fisheries managed with size limits require accurate estimates of age and growth that can be estimated through stable isotope sclerochronology. The age and growth of B. cochlidium at Playa Villarino, in north Patagonian gulf San Jos, Argentina was studied between 2005 and 2006. The 18O profiles of B. cochlidium shells analyzed in this study showed a maximum age of 5 y. Opercular rings and shell growth breaks, which record age in some other gastropods, gave higher counts than the number of years shown in isotope profiles. Thus, morphological proxies are unable to correctly asses age and growth in B. cochlidium. These results are useful to support and complement the first fisheries regulation of marine gastropods recently implemented in Argentina, aimed to conserve this vulnerable and valuable resource.
The edible marine gastropod Trophon geversianus shows a large geographic distribution along the southern tip of South America, inhabiting both rocky intertidal and shallow subtidal zones, with distinct behavioural responses to environmental stressful conditions (desiccation, temperature amplitude and high irradiation). Nevertheless, its reproductive biology has been poorly reported to date. We studied the gametogenic cycle of an intertidal rocky shore population from northern Patagonia (Argentina), in order to investigate the relation between gonadal changes and seasonal environmental variables. Mature individuals were taken monthly during an annual reproductive season and processed by standard histology procedures (haematoxylin and eosin). Adults of T. geversianus registered different gonadal maturation stages along the year, showing a marked seasonal variation without a resting period. The highest gamete evacuation season in both sexes was registered when the environmental stress was minimum (winter), while a greater number of individuals with gonads in proliferation and growth were predominant during maximum environmental stress (summer). The reproduction pattern presented an extended period of evacuation and a short phase of non-evacuation, associated to drastic seasonal environmental changes in the intertidal zone of Atlantic Patagonia. This information is useful to protect the resource and assure the sustainability of intertidal populations.
Recently, an Environmental Impact Assessment (EIA) was submitted for consideration to the National Environmental and Planning Agency (NEPA) of Jamaica by Noranda Jamaica Bauxite Partners II (NJBP II) in regards to a permit application to mine an area called SML-173 (Conrad Douglas & Associates Limited, 2020) (Fig. 1). SML-173 (SML standing for Special Mining Lease) is a part of Cockpit Country, which is the largest contiguous mesic limestone forest on the island and home to many endemic molluscan and other invertebrate species that cannot be found elsewhere on Jamaica. Cockpit Country has large reserves of aluminium-bearing soils (bauxite) and is constantly under threat of disturbance and mining despite protection measures. We provided critique and commentary to NEPA on the EIA, rejecting it for its inadequacies, including unclear reporting, lack of research and citations, unclear field methodologies and inaccurate results. We share a summary of some of these comments here to report on ongoing conservation issues and concerns for Jamaican terrestrial molluscs.
Marine gastropods are a popular seafood, abundant along coastal shores and healthy for human consumption. We studied variations in nutritional components during the gonadal cycle of Tegula patagonica, a novel gastropod resource protected by a recent artisanal fishery regulation. Similar to other marine gastropods consumed worldwide, T. patagonica was found to have a high protein content (mean ± s.d., 28.8 ± 15.4%) and a low lipid (1.36 ± 0.43%) and carbohydrate (1.7 ± 0.8%) content. The spawning peak was registered during spring and summer, concordant with increases in temperature and photoperiod, as observed for other gastropods from Atlantic Patagonia. According to our results, the optimal quality of T. patagonica for consumption is during the austral autumn, after the spawning season and when the gastropods have a high bodyweight and best nutritional contribution. Thus, this resource could be captured when its quality is optimal and its conservation promoted if established minimum catch sizes are respected.
Environments with strong gradients in physical conditions, such as rocky intertidal, induce animal morphological strategies to face them. The gastropod Trophon geversianus inhabit within the intertidal and subtidal habitats of Patagonian rocky shores. Although there is a wide knowledge of the phenotypic differences of this species regarding habitats (i.e., inter-tidal/subtidal), little is known about the interaction between habitat and latitude. Here, we studied form variation (size and shape) by using 3D geometric morphometric of T. gever-sianus shells from alive gastropods and analyzed the phenotypic effect from micro-scale (habitat), macro-scale (latitude), and the interaction habitat-latitude (site). Lastly, we tested the classification accuracy of the shape variable for each predictor variable and a synthetic variable (from a cluster analysis). We found that habitats and sites had the greatest influence on shape variation. Moreover, we found that the largest shell sizes were more likely to be located in subtidal habitats. Also, the size differences between sites were not negligible. Finally, habitat demonstrated the highest classification accuracy for shape, even higher than genetically determined (sex) and synthetic variables. We found that the gastropods from the intertidal habitat presented a globular morph with shorter spire and larger relative size of the shell aperture, while subtidal gastropod showed an elongated morph, with smaller aperture and longer spire. We present evidence of the complexity of size and shape variation in T. geversianus, highlighting that site-dependence on shape variation must be considered in geometric morphometrics studies at a latitudinal scale.
Gastropods shell shape has been proposed as a good indicator of environmental changes while geometric morphometric (GM) is a powerful tool to detect such changes. Shell shape pattern in adults of Buccinanops deformis was proved to be correlated with imposex incidence and maritime traffic in populations of Patagonia. We explore through GM the shell shape variation of B. deformis intracapsular embryos in pre-hatching stages of development, in two populations with contrasting maritime traffic and imposex incidence. Embryonic shell shape from polluted and unpolluted areas was significantly different in apex, lateral, aperture and siphonal channel. The same shell shape pattern was observed previously in B. deformis adult specimens. Our results demonstrate that the embryonic shell shape is an early biomarker that could be used as a tool to detect the response to environmental pollution studying abundant egg capsules laid in the field but protecting reproductive adults.
Based on 1,260 samples, the age and growth of purple whelk, Rapana venosa (Valenciennes) (Gastropoda:Muricidae) have been investigated. The samples were collected monthly during one year time (from February, 2004 to January, 2005) from the West Sea of Korea. The age of R. venosa was determined by the ring of the operculum analysis. The relationship between whelk's shell height and ring radius in each ring group was expressed as an equation of linear regression and later a correspondence in each ring formation was determined. Based on the monthly variations in the marginal index (MI) of the operculum, it was assumed that the ring of this species has been formed once a year during the period from July to August. The relationship between shell height and shell width was expressed by the equation SW = 0.7867 SH - 6.3988 (=0.8604); and between shell height and total weight by the equation (=0.8324). The purple whelk's spawning period was estimated through the fatness analysis and has occurred during the period from May to July. Obtained results suggests that the ring formation occurs once a year (in July) and the length of time period since the first ring has been formed on the operculum is approximately 13 months (1.08 year). The purple whelk's growth curves for shell height and total weight fitted to the von Bertalanffy's equation and were expressed as follows: .
The genus Trophon from southern South America is revised and restricted to ten valid species from among the 36 nominal species still currently used. In addition, a new species, Trophon parodizi from Patagonian waters, is described. Adult specimens of the new taxon are illustrated, described and compared with other living species of the same genus and similar geographic distribution. Redescription and re-illustration of types, based on material from several institutions around the world are provided for Trophon geversianus (Pallas, 1774), T. plicatus (Lightfoot, 1786), T. patagonicus (d'Orbigny, 1839), T. acanthodes Watson, 1882, T. pelseneeri Smith, 1915, T. amettei Carcelles, 1946, T. clenchi (Carcelles, 1953), T. wilhelmensis Ramirez-Bohme, 1981, and T. bahamondei McLean and Andrade, 1982. In addition, "Trophon" malvinarum Strebel, 1908, assigned to genera incerta, is also redescribed and illustrated.
Seasonality of reproduction in Buccinanops cochlidium, including mating, oviposition and embryonic development, was studied within a population in Patagonia. Mating was observed mainly during autumn and winter (March to October). Females carrying egg capsules were found between July and October when water temperature was 10°C, while development of embryos continued until February (the hatching peak) when water temperature was 18°C. All egg capsule masses were found attached to the shells of females 80-102 mm in length. The spawn consisted of 80 to 238 egg capsules, attached to the apertural callus of the shell. Linear regression analysis showed no significant relationship between female size and number of egg capsules. Each egg capsule contained 3100 eggs on average, with a mean egg diameter before cleavage of 227.5 μm. One to 20 embryos completed their development within each egg capsule by ingesting around 570 nurse eggs. The embryos followed a typical holoblastic spiralian division until gastrulation. During the 'veliger' stage the embryo consumed nurse eggs and formed a large rounded embryo up to 2 mm in diameter. After shell development the embryos hatched as crawling juveniles of 4.0 mm shell length through an opening opposite to the capsule stalk. There was an inverse relationship between the mean hatching shell size and the number of embryos per egg capsule. Under laboratory conditions development was completed in four months.rved.
Size at sexual maturity was studied in Zidona
dufresnei through analysis of gonadal tissue samples and secondary sexual characters. Individuals were sampled during two reproductive seasons (austral spring–summer) in the Mar del Plata area, Argentina. Gonadosomatic index was estimated for males and oocyte size frequency was used to estimate the stage of gonadal development in females. Gonadal maturity occurred prior to the development of secondary sexual characters. Size at first gonadal maturity in females was 12·8 cm shell length and in males 12·0 cm shell length, but size at which 50% of the population was mature was 15·7 cm in females and 15·0 cm in males. The results of this study could help to establish a minimal catching size.
Growth performance and mortality are two topics related closely to population dynamics of benthic macroinvertebrates. A new measure of overall growth performance for benthic invertebrate populations, the index ψ = log(maximum body mass/maximum age) is introduced. This index makes growth of populations and species comparable and is likely to be a species-specific feature. Differences in the index ψ among taxa and living modes as well as the relationship between growth performance and exploitation by man are analysed and discussed. Section 4 on mortality analyses the relationships between mortality and productivity in benthic invertebrate populations. An empirical model to estimate the natural mortality rate M of benthic populations from maximum body mass, maximum age and water temperature is constructed.
Movements of marked individuals of Nerita atramentosa Reeve, Austrocochlea constricta (Lamarck), Bembicium nanum (Lamarck), and Cellana tramoserica (Sowerby) were recorded at various sites in New South Wales in 1974 and 1975. A model of random movements during feeding at high tide was proposed, i.e., that animals wandered in random directions and the distances moved were exponentially distributed. Appropriate statistical tests for departures from such a model are given. The types of departure tested were non-random directions, non-exponentially distributed dis- tances, different distances in different directions, and correlated distances or directions of movement between days. With two exceptions, the movements of the animals over short periods were adequa- tely described by the assumption of random movements. One exception was A. constricta in one locality where movements of the sample were limited by it being in a large rock-pool and the other was the limpet C. tramoserica which displayed homing behaviour, so that the population could be divided into homers and non-homers. Movements of non-homing limpets were random.The mean distance moved by N. atramentosa was not significantly different from that of A. con- stricta. The mean distances moved by these two species were greater than those of B. nanum and the non-homing C. tramoserica, which were not different from each other. Adult and one-year old N. atramentosa did not differ significantly in mean distance moved, but both moved more than juveni- les. These patterns of movement are discussed with respect to hypotheses about feeding in these species.The model of movement was used to predict the effect of different percentage cover in small pools on the movement of A. constricta, which shows a preference for this micro-habitat. Increased availability of small pools reduced the mean distance moved by this species.
The whelk Buccinanops globulosum, a very common prosobranch mollusk in northern Patagonian, is the target of a new fishery in San Matías Gulf. Given certain biological characteristics making this species susceptible to overfishing, a study started in 2000 in order to collect data on demography and growth at age of this species, with the aim to design and to implement a provisional management plan.Mean density was estimated at 111 individuals m−2 (S.D. = 16.77). Females outnumbered males in most of the months (P < 0.05) and appeared laying egg capsules from November to January. The smallest female carrying egg capsules was 45.2 mm total conch length (n = 36). Recruitment peak was identified in January 2002 and January–February 2003. Early crawling juveniles had a mean size of 4.2 mm conch length (S.D. = 0.51, n = 60).A total of 450 individuals (263 females and 187 males) were examined for growth at age. Significant differences were found in the growth parameters between sexes (maximum likelihood method; χ = 92.34; gl = 3; P < 0.001). Growth of males was lower than growth of females.Commercial capture of whelks is done by diving using a bait of fish discarded or open living purple clams. Only adults up 4 cm are retained during the fishing operations in a net bag. During 2000–2004 the annual catch varied from 20 to 9200 kg. Fluctuations in landings have more often reflected market prices rather than changes in the abundance of the resource. If effort for this whelk increases it should be necessary to consider a period of no fishery at all in the reproductive/recruitment period in order to ensure the sustainability of the stock.
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