scholarly journals Sex ratio, gonadal and condition indexes of the Asiatic hard clam, Meretrix meretrix in Marudu Bay, Malaysia

2021 ◽  
Vol 22 (11) ◽  
Author(s):  
LADITAH DUISAN ◽  
Gazali Salim ◽  
JULIAN RANSANGAN
Keyword(s):  
Sex Ratio ◽  
Shell Length ◽  
Condition Index ◽  
Habitat Destruction ◽  
Hard Clam ◽  
Meretrix Meretrix ◽  
Artificial Breeding ◽  
Artificial Seed ◽  
Hard Clams ◽  
Species Being

Abstract. Duisan L, Salim G, Ransangan J. 2021. Sex ratio, Gonadal and Condition indexes of the Asiatic Hard Clam, Meretrix meretrix in Marudu Bay, Malaysia. Biodiversitas 22: 4895-4904. Asiatic hard clam, Meretrix meretrix is one of the important shellfishery resources in Marudu Bay, Sabah, Malaysia. It is among the most popular clam species being widely traded in the local wet markets around Sabah, Malaysia. Unfortunately, the shellfishery management for this species has not been well established. In addition to overexploitation, habitat destruction is also one of the significant threats to this species due to the extensive land use of the coastal areas in Sabah. Hence, conservation and breeding efforts for this species are greatly required. Therefore, the current study was conducted to examine the sexual maturity of the clam with respect to shell length classes for artificial seed production purposes. For this study, a total of 86 clam specimens were randomly collected from mudflats in Marudu Bay. The specimens were utilized for gonad histological and condition analyses. The clams were grouped into three shell length classes; (3.00-4.99) cm, (5.00-6.99) cm, and (7.00-8.99) cm prior to the analyses. Results showed the natural stock of the Asiatic hard clams in Marudu Bay was dominated by females (1.39:1) over males with no hermaphroditism observed. The gonadal index was recorded higher among clams with shell lengths between 5.00 and 6.99 cm. The condition index analysis also recorded high (>4.0) for clams in all the shell length classes. The findings of this study suggest that the clams with shell lengths between 5.00 cm and 7.00 cm are already fully matured and can be utilized as a broodstock candidate for an artificial breeding program in the hatchery.

scholarly journals Dredging-induced shell damages to hard clam (Meretrix meretrix): a Malaysian case study

2018 ◽  
Vol 32 ◽  
pp. 1 ◽  
Author(s):  
Tan Kar Soon ◽  
Julian Ransangan
Keyword(s):  
Shell Length ◽  
Fishery Management ◽  
Sampling Methods ◽  
Hard Clam ◽  
Meretrix Meretrix ◽  
Community Based ◽  
Awareness Programs ◽  
Negative Impacts ◽  
Hard Clams

The hard clam (Meretrix meretrix) is a popular edible shellfish in South and Southeast Asia, being heavily exploited by hand dredging in Marudu Bay, Malaysia. The current study was performed to evaluate the shell damages caused by this artisanal dredging gear. Samplings were conducted in triplicates at two sites using both hand dredging and hand collecting (control) sampling methods. The shell length and total weight, damage areas and breakage patterns of each clam were recorded. A questionnaire survey was conducted with local bivalve harvesters to gather information on the fishing pressure in Marudu Bay. Results revealed that the efficiency (fishing yield) of hand dredging gear was three times higher than hand collecting. However, hand dredging gear causes lethal shell damages to small hard clams (<3cm in shell length). Hard clam harvesting is the main occupation of most fishermen in Kg. Popok, but most of them do not comply with the minimum harvesting size established by the fishery department. Moreover, most of the stakeholders are not aware of the negative impacts of hand dredging to the sustainability of the hard clam fishery in Marudu Bay. Therefore, organizing more awareness programs combined with introducing community-based fishery management are highly recommended to promote the sustainability of this artisanal fishery.

Freshwater pearl culture in China.

2020 ◽  
Author(s):  
Lin Cao
Keyword(s):  
Shell Length ◽  
Culture Period ◽  
Production Cycle ◽  
High Quality ◽  
Host Fish ◽  
Genetic Quality ◽  
Operative Care ◽  
Artificial Breeding

Abstract Artificial breeding of freshwater pearl mussels is widely used to improve the yield of pearl culture. All phases of the production cycle, including collection and culture of the broodstock, release of the glochidia, provision of the host fish for glochidia to attach to, and collection of mussel seeds, can be controlled artificially. The advantages of artificial breeding are that it can help to produce high quality pearls and improve the genetic quality of pearl mussels. Collected mussel seed are transferred from holding jars into small 200 µm mesh baskets (10 cm diameter x 5 cm). Each basket was supplied individually with 0.1-0.2 L of water per minute. When the mussels' shell length reaches over 10 cm, they can be operated to culture pearl. After post-operative care the implanted mussels are stocked in ponds. The mussels are kept in nylon bags (2 mussels per bag) and are hung from bamboo or PVC pipes and placed in ponds at 1 m depth. Periodical checking of mussels, with removal of dead ones and cleaning of bags, is required throughout the culture period of 12-18 months.

Identification and expression of a putative LPS-induced TNF-α factor from Asiatic hard clam Meretrix meretrix

2011 ◽  
Vol 39 (2) ◽  
pp. 865-871 ◽  
Author(s):  
Hong-jun Li ◽  
Qing Yang ◽  
Xiang-gang Gao ◽  
Hao Su ◽  
Juan Wang ◽  
...  
Keyword(s):  
Hard Clam ◽  
Meretrix Meretrix ◽  
Tnf Α

Variations in eastern oyster (Crassostrea virginica) sex-ratios from three Virginia estuaries: protandry, growth and demographics

2012 ◽  
Vol 93 (2) ◽  
pp. 519-531 ◽  
Author(s):  
Juliana M. Harding ◽  
Eric N. Powell ◽  
Roger Mann ◽  
Melissa J. Southworth
Keyword(s):  
Sex Ratio ◽  
Shell Length ◽  
Sex Ratios ◽  
Eastern Oyster ◽  
Reproductive Capacity ◽  
Older Individuals ◽  
Population Demographics ◽  
Disease Mortality ◽  
Predominantly Female ◽  
Male To Female

Oyster population reproductive capacity and dynamics are controlled at the most basic level by the observed sex-ratios. Since oysters are sequential, protandric hermaphrodites the population sex-ratio is related to the demographics (shell length, age, and biomass). Oysters were collected from June through to August 2008 at twelve bars in the James, Rappahannock and Great Wicomico Rivers, Virginia, USA. Bars were aggregated into five groups on the basis of similar age–length relationships. Sex-ratios (fraction female), age–length, and biomass–length relationships were determined for each group. The fraction female increased within increasing shell length, age, and biomass at all sites. Simultaneous hermaphrodites were rarely observed. Group specific differences in shell length (SL, mm) and age (yr) for the timing of the protandric shift were observed with the earliest shift from male to female occurring at ~60 mm SL and ~1.6 yr. The proportion of females observed in the larger or older individuals was at least 70–80%. Sex-ratios from summer 2008 were used to develop sex–length, sex–age, and sex–biomass keys that were applied to autumn-survey data from 2006, 2007, 2008 and 2009. In these years, sex-ratios by shell length and age were strongly biased towards males while the sex-ratio by biomass was strongly biased towards females. Disease mortality compounds natural and fishing mortality resulting in age/size specific cropping yielding truncated population demographics and an earlier protandric shift in populations on the extremes of the range examined. Regardless of location, market (>76 mm SL) oysters are predominantly female.

scholarly journals First observations of hermaphroditism in the patellid limpet Patella piperata Gould, 1846

2019 ◽  
Vol 99 (7) ◽  
pp. 1615-1620
Author(s):  
Ricardo Sousa ◽  
Paulo Henriques ◽  
Joana Vasconcelos ◽  
Graça Faria ◽  
Rodrigo Riera ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Direct Effect ◽  
Shell Length ◽  
Histological Analysis ◽  
Size Classes ◽  
Sequential Hermaphroditism ◽  
North Eastern ◽  
Intermediate Size ◽  
Transitional Forms ◽  
Management And Conservation

AbstractHermaphroditism is thought to be an advantageous strategy common in marine molluscs that exhibit simultaneous, sequential or alternating hermaphroditism. Several species of patellid limpets have previously been shown to be protandrous hermaphrodites. The present study aimed to confirm whether this phenomenon occurs in Patella piperata. Transitional forms of simultaneous protandrous hermaphroditism were found in intermediate size classes of P. piperata, in Madeira (North-eastern Atlantic). Sequential hermaphroditism was confirmed after histological analysis. The overall sex-ratio was biased towards females but approached similar proportions in the larger size classes. Analysis of size at sex change showed that at a shell length of 36 mm 50% of the population probably have changed sex. The results reported confirm the occurrence of sequential hermaphroditism. These findings are of utmost importance to the understanding of the reproductive biology of this species with direct effect on management and conservation of this traditionally harvested limpet.

Mining single nucleotide polymorphisms from EST data of hard clam Meretrix meretrix

2010 ◽  
Vol 2 (S1) ◽  
pp. 69-72 ◽  
Author(s):  
Hongjun Li ◽  
Dan Zhu ◽  
Xianggang Gao ◽  
Yun-feng Li ◽  
Jian Wang ◽  
...  
Keyword(s):  
Single Nucleotide Polymorphisms ◽  
Hard Clam ◽  
Meretrix Meretrix ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide

Toxicological responses of the hard clam Meretrix meretrix exposed to excess dissolved iron or challenged by Vibrio parahaemolyticus

2014 ◽  
Vol 156 ◽  
pp. 240-247 ◽  
Author(s):  
Qing Zhou ◽  
Yong Zhang ◽  
Hui-Fang Peng ◽  
Cai-Huan Ke ◽  
He-Qing Huang
Keyword(s):  
Vibrio Parahaemolyticus ◽  
Hard Clam ◽  
Meretrix Meretrix ◽  
Dissolved Iron
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