Growth and reproductive cycle of Donax trunculus L., (Mollusca: Bivalvia) off Faro, southern Portugal

doi:10.1016/S0165-7836(99)00017-X

Fisheries Research

Volume 41, Issue 3, July 1999, Pages 309-316

https://doi.org/10.1016/S0165-7836(99)00017-X Get rights and content

Abstract

The shell growth and reproductive cycle of Donax trunculus (Mollusca: Bivalvia) from southern Portugal were studied from December 1993 to November 1994. Both the acetate peel method and quantification of surface growth rings were used to establish age and estimate growth rate. Widely spaced growth bands were formed in spring and summer whilst narrowly spaced bands were deposited in late summer and early autumn. No cessation of growth was observed during the winter. The von Bertalanffy growth curve estimated from the internal bands did not differ significantly from that obtained from the surface rings. However, the age of clams can be determined more accurately from acetate peels than directly from surface rings. Laboratory experiments demonstrated that periodicity of the deposition of microgrowth bands was related to an innate rhythm. Gonadal development was monitored using standard histological methods. Both males and females showed synchronism in gonadal development. The gametogenic cycle began in late November and ended in late August. Spawning occurred between March and August with two major spawning phases: March and May–August. D. trunculus reached maturity during the first year of life.

Introduction

Donax trunculus is an Atlantic–Mediterranean warm-temperate species. In the Atlantic it has been recorded from Senegal to the French coast (Tebble, 1966). It inhabits the high-energy environment of exposed sandy beaches, where it forms extensive, dense beds. It is the most inshore surf clam species in Portuguese waters, occurring to 6 m depth, with higher densities between 0 and 3 m depth. It is an excellent burrower, which makes it well adapted to life in the swash zone.

Along the south coast of Portugal, D. trunculus is one of the most important commercial species exploited by an artisanal fleet. Actually a total of 60 boats are involved in this fishery. These boats vary in length from 4 to 15 m, with engines of 17–150 Hp. Unfortunately no reliable statistics concerning catches are available since fishermen were not obliged to declare their catches until 1998. However in 1997, a catch of 425 t of D. trunculus, worth PTE128 million was estimated. Despite its economic importance, its biology in this region has not hitherto been described. This study reports on the rate of growth, life span and age/size at first maturity, of a population of Donax trunculus, off Faro, southern Portugal, by way of a comparison with other populations at different geographical locations.

Section snippets

Materials and methods

Samples were collected by dredging off Faro, from December 1993 to November 1994, at approximately monthly intervals.

Growth

Fig. 1 illustrates acetate peels from sections through the shell of D. trunculus. According to Taylor et al. (1973)these shells are composed of three layers, an outer composite prismatic layer, middle crossed lamellar layer, and an inner homogeneous/complex crossed lamellar layer (Fig. 1(A)).

The growth bands in the outer layer run parallel to the growing edges of the shell, and appear as thin dark lines, with wider transparent regions, i.e. the growth increments, between (Fig. 1(B)). In some

Growth

Rapid shell growth occurred in spring and summer, when wide microgrowth increments were deposited, whilst slow growth occurred during late summer and early autumn with the deposition of narrow growth increments and the formation of a well-defined annual growth ring. Surprisingly, we did not note a period of cessation of growth through the winter months. In fact, D. trunculus renewed growth in November which then continued until the following October. This is a different pattern of seasonal

Acknowledgements

We would like to thank three anonymous referees whose suggestions greatly improved the manuscript. We also thank the staff of IPIMAR/CRIPSul for collecting the samples and the crew of NI/DONAX for their skilful handling of the boat and fishing gears. M.B. Gaspar was funded by JNICT – PROGRAMA CIÊNCIA and PRAXIS XXI.

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This study was the first attempt to characterize the recreational harvesting of the wedge clam (Donax trunculus). For this purpose, 403 face-to-face interviews were performed in the summers of 2018 and 2019 in southern Portugal. The majority of the harvesters frequented the selected beaches during holidays and collected wedge clams as a hobby for an appetizer. The respondents reported an inter-annual variation in their catches of wedge clam with a decreasing abundance in 2018 followed by a recovery in 2019, but with more recreational harvesters collecting undersized individuals. Although most harvesters declared to consume D. trunculus, only a few bought wedge clams being the clams’ size a secondary factor in their valorization. The majority of the recreational harvesters did not know the species' minimum conservation reference size nor the legally allowed maximum daily catch. It was estimated that recreational harvesters can collect 13 tonnes of wedge clams during the summer season along the southeastern coast of Algarve. Even though manual harvesting is not an efficient fishing technique, the lack of selectivity of harvesters can eventually compromise the resilience of D. trunculus populations. Despite most respondents affirmed to get informed about marine biotoxins, most surveys were done during periods of interdiction for shellfish harvesting. The present results revealed that the population is still unaware of the health risks of consuming shellfish contaminated with biotoxins. Educational activities and awareness campaigns are required to further inform recreational harvesters about the regulations in force for this activity and the sanitary threats of marine biotoxins.
Reproductive cycle of two marine sentinel bivalve species (Donax trunculus and Scrobicularia plana) in the Agadir bay, Southern Morocco
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The reproductive cycle of two marine sentinel bivalve species, Donax trunculus and Scrobicularia plana, was studied from monthly random samples. A total of 1200 specimens were collected from January to December 2019 in two different sites of Agadir bay (Agadir beach; AG and Oued Souss estuary; OS). The analysis was based on the temporal variation of condition index, gonadal index, sex-ratio, and maturity stages of gonads through histological observation. We also studied the environmental parameters and their impact on the reproduction of those species. Results indicate that the sex-ratio was slightly unbalanced in favor of females in AG (
= 1: 1.3) and males in OS (
= 1: 0.9). Stages of gonad development maturity were identified as five stages: undifferentiated, developing, ripe, spawning, and spent. The spawning period occurred from March to July for S. plana, and from May to August for D. trunculus; the two species had one annual gonadal cycle. During the microscopic observations, no parasitic infection was detected. The physico-chemical parameters; especially temperature, dissolved oxygen, pH, and precipitation, influenced the gonads maturity and the spawning process in the studied species.
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The article aims to quantify a multiyear ocean temperature change at a shallow (5 m) coastal site in the northeastern Adriatic. Measurements were taken between May 2014 and May 2021 with an hourly resolution, allowing for an extraction of temperature variations over longer-term, seasonal, synoptic, quasi-diurnal and hourly timescales. As expected for shallow waters, the seasonal influence is prevalent, while diurnal changes are quasi-persistent throughout the year. Marine heat waves and cold spells are the strongest during spring and summer months. Non-seasonal changes mostly guide longer-term (>10 days) variability, yet rapid temperature changes reach 2 ^°C/h during stratified seasons. Such rapid changes may impact benthic communities and the physiology of marine species, including bivalves. This is especially important in the era of global warming, in which environmental conditions are already pushed towards their thresholds, and where high-frequency variability analyses can be useful in introducing a precautionary approach for local climate change adaptation.
Influence of wind, rainfall, temperature, and primary productivity, on the biomass of the bivalves Spisula solida, Donax trunculus, Chamelea gallina and Ensis siliqua
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Citation Excerpt :
The species E. siliqua, in the Algarve, show an extensive inactive phase between July and October, with gametogenesis beginning in November and spawning period occurring between April and May (Gaspar and Monteiro, 1998). Thus, in all cases and considering the estimated growth equations, within one year after settlement all the individuals of bivalve species studied would have grown to a capturable size during IPMA’s bivalve surveys (Gaspar et al., 1994, 1995; 1999; 2004) (Fig. 4). Multiple linear regression was used to investigate the effect of the environmental variables on species biomass of the following year (using SAS/STAT®).
Coastal bivalve populations are characterized by large temporal fluctuations, driven by recruitment success dependent on environmental conditions. The present study evaluated the relationship of rainfall, chlorophyll-α, sea surface temperature (SST) and wind, with the biomass of four commercial bivalve species (Spisula solida, Donax trunculus, Chamelea gallina and Ensis siliqua) that occur both along the Barlavento (western region), and the Sotavento (eastern region), along the South coast of Portugal, between 1999 and 2011.
Multiple regression models were used to test two hypotheses: a) the association between environmental conditions three months prior to the spawning period and the biomass in the following year (response variable) and b) the association between environmental conditions during the spawning season plus one month and the biomass in the following year. Wind was not included in the model to test a).
The environmental variables considered were not important for E. siliqua. In the period prior to spawning, temperature was significant for S. solida (both study areas), rain for D. trunculus and C. gallina (western area) and chlorophyll-α for C. gallina (western area). All the correlations were positive.
During the spawning period, rain was significant for all three species but with different trends. The correlation with rain in months early in the spawning season was positive for S. solida (both areas) and D. trunculus (western area). The correlation with the rain in months towards the end of the spawning period was negative for D. trunculus, and C. gallina (western area). Chlorophyll-α in months at later stages of spawning was significant and positive for D. trunculus (both areas) and C. gallina (western area). The wind, expressed as an index developed to indicate the overall occurrence of winds blowing parallel to the coast (assumes to favour the retention of larvae in appropriate environments), was negatively correlated with biomass for mid to late spawning season for S. solida (eastern area) and D. trunculus (western area). For C. gallina there was a positive correlation with wind early in the spawning season. The SST was not an important variable during the spawning period with the exception of D. trunculus where the temperature at mid spawning season was significant with a negative correlation in the western coast and positive in the eastern coast.
This study highlighted the annual spatial distribution of four commercially important bivalves and how environmental factors are likely to play an important role on both biomass and location of the fishing beds. Monitoring of the environmental variables could provide information to predict biomasses of bivalve species, an important tool for its management, as well as predict trends and plan strategies in response to global environmental changes.
Assessment of reproductive cycle, parasitism and biological indices of the wedge clam Donax trunculus along the Taghazout coastline (on the Moroccan Atlantic Coast)
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Citation Excerpt :
Also, Badino and Marchionni (1972) and Mouëza and Frenkiel-Renault (1973) found a sex ratio of 1:1 in D. trunculus. However, Gaspar et al. (1999) found that the proportion of males has increased in the D. trunculus population in Portugal and this could be explained by differential growth or mortality resulting from the spawning effort. Indeed Boussoufa et al. (2015) observed that the sex ratio in D. trunculus from Tunis Bay was in favor of males.
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Fisheries Research

Abstract

Introduction

Section snippets

Materials and methods

Growth

Growth

Acknowledgements

References (24)

Seasonal changes in tissue weight and biochemical composition for the bivalve Donax trunculus L. on the Algerian coast

J. Exp. Mar. Biol. Ecol.

Observations on the biology of Donax trunculus and Donax vittatus at ell d'Oléron (French Atlantic Coast)

Mar. Biol.

Neurosecretion and gonad maturation in a population of Donax trunculus L. from Leghorn (Italy)

Bull. Zool.

Reproduction de Donax trunculus sur la côte Atlantique marrocaine

Cah. Biol. Mar.

Contribution á l'etude des populations du genere Donax: la populations de D. trunculus L. (Mollusca, Bivalvia) de Mehdia (Maroc)

Ann. L'Inst. Océan., Paris

Croissance saisonniére du bivalve Donax trunculus (L.) en Mediterranée nordoccidentéle (France)

Malacologia

Age and growth rate of the clam Spisula solida L., from a site off Vilamoura, south Portugal, determined from acetate replicas of shell sections

Sci. Mar.

Reproductive cycles of the razor clam Ensis siliqua and the clam Venus striatula off Vilamoura, southern Portugal

J. Mar. Biol. Ass. UK

Aspects de la dynamique des populations de Donax vittatus Donax trunculus et en baie de Douarnenez

Ann. L'Inst. Océan., Paris

Recherche sur la sexualité des Mollusques Bivalves

Bull. Biol. Franco-Belgian

Aspectos de la dinamica de población de Donax trunculus (Linnaeus, 1758) (Bivalvia: Donacidae) en la rı́a de El Barquero (Lugo, NO Espana)

Invest. Pesq.

Cited by (107)

Recreational harvesting of the wedge clam (Donax trunculus) in southern Portugal: Characterization of the activity based on harvesters’ perception and local ecological knowledge

Reproductive cycle of two marine sentinel bivalve species (Donax trunculus and Scrobicularia plana) in the Agadir bay, Southern Morocco

Near-surface ocean temperature variations across temporal scales in the coastal eastern Adriatic

Influence of wind, rainfall, temperature, and primary productivity, on the biomass of the bivalves Spisula solida, Donax trunculus, Chamelea gallina and Ensis siliqua

Assessment of reproductive cycle, parasitism and biological indices of the wedge clam Donax trunculus along the Taghazout coastline (on the Moroccan Atlantic Coast)

Comparison and Optimal Prediction of Goptimal prediction of growth of Babylonia areolata and B. lutosa