Mm Of Shell Length Research Articles

Historical Reconstruction of Biomass of Panopea globosa from the Southwestern Coast of Baja California Peninsula, Mexico: A New Perspective for Geoduck Fishery Management

In this study, fishery-independent data were used to analyze changes in average density and biomass of Panopea globosa between 2007 and 2018. Different statistical estimators based on the probabilistic density function, such as Gaussian and generalized distributions, were used, all of them associated with the spatial patchy distribution of the geoduck clam. Both average density and biomass showed a dramatic decline throughout the study period, decreasing from 31 geoducks/50 m2 (2007) to 10 geoducks/50 m2 (2018) and from 126,000 to 35,000 t, respectively. In addition, a high harvest of individuals greater than 175 mm of shell length was observed, increasing the possibility of recruitment overfishing. Finally, a Kobe phase chart applied to P. globosa fishery in Bahía Magdalena showed that the stock status was identified as overfished.

Morphological and population changes of the cockle Cerastoderma glaucum in Lake Qarun, Egypt, may be driven by accelerated environmental deterioration

The cockle Cerastoderma glaucum represents a significant element of the benthic community in Lake Qarun, Egypt. The population of this species has severely declined in the lake. For stock position assessment, cockles were collected in the winter of 2008 and 2018. The body size (length-frequency) distributions considerably varied among the collections. A single peak at 14 mm was present in 2008, and two peaks appeared ten years later (one at 13mm and another at 19 mm). The total weight, shell weight and flesh weight of individuals collected in 2008 exhibited isometric increase with shell length (SL). For samples collected in 2018, flesh weight increase was slower than shell length, indicating negative allometric growth. When 50% of the population achieved maturity (SM50), their sizes were 7.7 and 7.4 mm of SL for 2008 and 2018 collections, respectively, consistent with the sexual maturity being related to size rather than age. The overall sex ratios did not significantly differ from unity (1:1). The results of this study suggest that the species is sensitive to salinity changes and water pollution, with larger individuals being more resistant than the smaller ones. This may have implications for species’ long-term reproduction and density.

Sex-related genes expression in juveniles of red abalone, Haliotis rufescens (Swanson, 1822)

The red abalone, Haliotis rufescens (Swanson 1822), is an important species for commercial aquaculture in Mexico, with annual production levels around 68 t. Not surprisingly, there is great interest in increasing production and its cultivation success. In order to have a better understanding of the genes involved in the sexual differentiation, this study analyzed the early differential expression of eight sex-related genes (VCP 2.2, VERL, VTGI, DMRT1, FP, LYS, SARIP, TEKT A1) by RT-qPCR in abalones from 5 to 45 mm of shell length. Sex identification was evaluated using VERL and LYS genes expression levels. These genes differentiated females and males from 16 mm of shell length and above. All eight sex-specific genes showed expression in all organisms. However, their level was higher in the sex group to which they correspond. In contrast, differential expression levels occurred in individuals with a shell length of 26–35 mm and 36–45 mm. These results suggest that sex gene expression is not entirely sex specific, and sexual differentiation in red abalone occurs between 16 and 25 mm of shell length. More studies are needed to determine the function of these genes in the sex that they are not associated with.

선발 3세대 북방전복의 성장형질에 대한 가계변이 및 유전모수 추정

본 연구에서는 전복의 성장형질에 대한 가계변이를 비교분석하기 위한 목적으로 2011년에 생산된 선발 3세대 북방전복 5,334마리에 대한 18개월령 성장형질인 각장, 각폭 및 중량의 전체 계측자료를 이용하여 유전모수와 육종가를 추정하였으며, 그 중 개체수가 많은 상위 10가계의 865마리 대한 가계변이를 조사하였다. 가계효과를 추정하기 위해 개체모형에 근거한 선형모형을 이용하였고, 유전모수 및 육종가는 생산시기를 고정 효과로 처리하고, EM-REML algorithm을 전산 프로그램화한 REMLF90을 이용하여 최적선형불편예측법에 의해 추정하였다. 본 연구에서 조사된 18개월령 북방전복의 표현형에 있어 각장, 각폭 및 중량의 전체평균은 각각 54.5 mm, 36.8 mm 및 21.3 g로 나타났고, 중량의 변이계수가 51.0%로 나타나 각장의 21.1% 및 각폭의 20.7% 보다 자료의 변동성이 크게 나타났다. 개체수가 많은 상위 10가계를 대상으로 각장과 중량의 관계를 산점도로 표시한 결과 상관관계식이 TW = <TEX>$0.0002SL^{2.8796}$</TEX> (<TEX>$R^2$</TEX> = 0.9864) 과 같이 지수곡선식으로 추정되었다. 가계효과에 있어서는 각 가계별로 유의적인 차이를 보였으며 (p < 0.05), 각장, 각폭 및 중량의 유전력은 각각 0.370, 0.382 및 0.367로 중도의 유전력을 보여 개체선발 보다는 가계선발이 유리할 것으로 사료된다. 또한 각 형질 간 상관계수는 매우 높은 정의 상관관계를 보여 한 형질만의 개량으로 다른 형질의 개량효과를 기대할 수 있을 것으로 판단된다. 추정된 각장 및 중량의 육종가를 토대로 개체수가 많은 상위 10가계에 대한 각 개체별 분포와 순위를 조사하기 위해 표준화육종가로 변환하여 이용하였으며, 각장을 기준으로 상위 5.4%의 개체 수는 152마리, 하위 5.4%의 개체 수는 8마리로 조사되었고, 중량의 경우 상위 5.4%의 개체 수는 164마리, 하위 5.4%의 개체 수는 1마리로 조사되었다. 이와 같이 가계간의 표현형 및 유전적인 다양한 변이를 확인 할 수 있었고, 다음 세대 생산을 위한 모집단의 유전모수와 육종가를 추정하여 선발과 교배에 적절히 이용한다면 보다 나은 육종효과를 기대할 수 있을 것으로 사료된다. The purpose of this paper is to compare and analyze family variations for growth-related traits of Pacific abalone, Haliotis discus hannai. Genetic parameters and breeding values were estimated using all measurement data like shell length, shell width, and total weight as 18-month-old growth traits of 5,334 individuals of selected third generation's Pacific abalone produced in 2011. Family variations of 865 individuals of the upper 10 families with the largest number were inspected. Overall mean in phenotypic traits of 18-month-old Pacific abalone which was investigated in this study showed 54.5 mm of shell length, 36.8 mm of shell width and 21.3 g of total weight respectively. And, variation coefficient of total weight was 51.0%, so variability of data was shown to be higher than 21.1% of shell length and 20.7% of shell width. The family effects showed significant difference by each family (p < 0.05), and heritability of shell length, shell width, and total weight was medium with 0.370, 0.382, and 0.367 respectively. So it is considered that family selection is more advantageous than individual selection. On the basis of breeding values of estimated shell length and total weight, to investigate distribution and ranking by each individual about the upper 10 families with the largest number of individuals, the values were used by being changed into standardized breeding values. Based on shell length, it was investigated that the individual number of the upper 5.4% is 152 and the number of the lower 5.4% is 8. In case of total weight, it was inspected that the individual number of the upper 5.4% is 164 and the number of the lower 5.4% is 1. Like these, phenotypic and genetic diverse variations between families could be checked. By estimating genetic parameters and breeding values of a population for production of the next generation, if they are used properly in selection and mating, it is considered that more breeding effects can be expected.

Reproductive biology of the cockle Cerastoderma glaucum (Bivalvia:Cardiidae) from Lake Qarun, Egypt

The cockle Cerastoderma glaucum is an important component of the benthic community in Lake Qarun, Egypt. Reproduction and gonad development in this species were investigated during the period from February 2008 to May 2009. Reproductive maturity was estimated by assessment of length–weight relationship, gonad index and microscopic examination of gonadal smears and sections. Results indicate lack of periodicity in the sexual cycle. An annual pattern of four spawnings was recorded. The depletion of ripe gametes during spawning was rapidly compensated by the onset of gametogenesis. Monthly changes in flesh and gonad weight reflect reproductive cycle with weight loss during spawning. C. glaucum is a gonochoric species without any hermaphrodites or sex reversals. The overall samples presented a male biased sex ratio (F:M=1:1.29). The size at which 50% of the population reached maturity was 9.6 and 8.5mm of shell length for females and males, respectively.

31개월령 북방전복, Haliotis discus hannai의 성장형질에 대한 선발반응 추정

본 연구에서는 31개월령 북방전복의 성장형질에 대한 선발반응을 추정하기 위해 2008년에 생산된 2세대 육종전복의 모집단 6,858마리와 다음 세대 생산을 위해 최종 교배지침에 포함된 614마리의 자료를 이용하였다. 각 형질별 전체평균은 각 장, 각폭 및 중량이 각각 76.31 mm, 49.48 mm 및 56.90 g로 조사되었고, 중량의 변이계수가 28.70%로 나타나 다른 형질에 비해 자료의 변이가 가장 크게 나타났다. 각장, 각폭, 중량 및 비만도에 있어서 성과 성숙도의 효과에 대한 분산분석을 실시한 결과 비만도를 제외한 모든 형질에서 고도의 유의성이 인정되었으며 (p < 0.01), 성의 효과는 비만도를 제외한 모든 형질에 있어서 수컷보다 암컷이 유의적으로 높게 나타났다. 각 형질별 육종가와 표현형가의 상관관계는 각장, 각폭 및 중량에 있어서 순위상관계수와 단순상관계수의 범위가 0.63에서 0.71로 대체적으로 낮게 나타나 육종가와 표현형가의 상관관계를 더 높인다면 보다 효율적인 개량을 도모할 수 있을 것으로 사료되며, 선발반응 예측치 즉, 기대되는 유전적 개량량은 각장, 각폭 및 중량이 각각 9.6%, 9.5% 및 26.1%로 나타났다. 따라서 다음 세대에 있어서 보다 높은 선발반응을 기대하기 위해서는 선발의 정확도는 물론 최종교배를 위해 선발되는 개체의 비율과 선발강도를 적절히 고려하여야 할 것으로 사료된다. This study was conducted to estimation the selection response for growth-related traits in 31-month old of Pacific abalone, Haliotis discus hannai were born in 2008. In overall mean of surveyed traits and standard deviation showed <TEX>$76.31{\pm}7.247$</TEX> mm of shell length, <TEX>$49.48{\pm}5.307$</TEX> mm of shell width and <TEX>$40.96{\pm}6.80$</TEX> g of total weight. The effect of sex and maturity were statistically significant in all traits include out a condition factor (p < 0.01). And In effect of sex, female were higher than male in all traits excepting condition factor, significantly. In correlation between breeding value and phenotypic value by each traits, showed rank correlation coefficient and simple correlation coefficient, which represented low positive correlation. A hopeful genetic improvement to the next generation showed 6.96 mm of shell length, 4.47 mm of shel width and 12.93 g of total weight. Therefor, It is considered that if considering properly selection intensity and selection ratio, efficient improvement could be made.

Life history traits of the exploited limpet Patella candei (Mollusca: Patellogastropoda) of the north-eastern Atlantic

Life history traits of Patella candei were studied for the first time, including weight versus length relationship, growth, age structure, sexual maturity, recruitment pattern, mortality rates and yield and biomass-per-recruit of an exploited population in Madeira Island, north-eastern Atlantic using monthly length–frequency data from January to December 1999. The growth pattern of P. candei showed positive allometric nature of growth (b &gt; 3, P &lt; 0.05). The estimated growth parameters showed an asymptotic length (L∞) and growth coefficient (K) estimated at 80.81 mm and K at 0.32 year−1 with a growth performance index (φ′) calculated as 3.32 based on the collected data. This species is moderately long-lived reaching up to 9.36 years and achieving sexual maturity at 36.7 mm of shell length. The recruitment pattern was continuous, displaying a major peak event per year, occurring in January (25.12%). The estimated total mortality rate (Z) was 1.79 year−1 while natural mortality rate (M) was 0.55 year−1 and fishing mortality rate (F) was 1.24 year−1. The probability of capture shows that the length at first capture (Lc) was 42.7 mm, the exploitation rate (E) 0.693 and the maximum allowable limit of exploitation (Emax) was 0.779 for the highest yield. The exploitation rate was less than the predicted Emax values, showing that the stock of P. candei was found to be under-exploited in the investigated area; however, its slow growth and long life make it extremely vulnerable to over-exploitation.

Perkinsus marinus in pleasure oyster Crassostrea corteziensis from Nayarit, Pacific coast of México

Culture of the pleasure oyster Crassostrea corteziensis is emerging as an alternative to the Pacific oyster ( Crassostrea gigas) for oyster producers, who face severe mortalities since 1997 in Northwest México. For determining the health status of this species, we conducted a histopathological analysis of cultured populations from two estuaries in the Pacific coast of México. Macroscopical analysis revealed animals with transparent and retracted mantle. Histopathological analysis of these specimens showed tissue alterations and parasitic forms consistent with Perkinsus sp. infection. Stages of the parasite identified included tomont and trophozoites with an eccentric vacuole characteristic of Perkinsus spp. Pieces of tissues of infected oysters were incubated in Fluid Thioglycollate Medium (FTM) resulting in blue–black hypnospores after incubation. The identity of the parasite was confirmed by species specific PCR-based assay in DNA samples from oysters, tissue fractions from FTM cultures, and deparaffined samples with Perkinsus-like parasite detected by histology. Sequencing of positive amplified fragments (307 bp) showed a sequence similar to Perkinsus marinus strain TXsc NTS ribosomal RNA gene (100% coverage and 98% identity, GenBank Accession No. AF497479.1) and to P. marinus, Genomic DNA, (100% coverage and 97% identity, GenBank Accession No. S78416.1). The prevalence of P. marinus varied from 1 to 5% in Boca del Camichín and from 1 to 6% in Pozo Chino. In general, the intensity of infection was moderate. The infection was observed in oysters from 31 to 110 mm of shell length. This is the first record of P. marinus in oysters from the North America Pacific coast and the first record in C. corteziensis. The origin of this parasite in the area is unknown, but it may be associated to introductions of Crassostrea virginica from the East coast of United States of America or Gulf of México.

Light-related behaviour of the zebra mussel (Dreissena polymorpha, Bivalvia)

We studied the impact of light of various intensities (0.1-100 lux) and wavelengths upon zebra mussel behaviour in the laboratory. Mussels selected dark attachment sites rather than illuminated ones. The response of large individuals (>10 mm of shell length) was stronger than that of small ones (<10 mm). Mussels avoided even very dim illumination (as low as 0.1 or 1.2 lx, in the case of large and small individuals, respectively). All mussels avoided light of various wavelengths (red, green, blue) equally. Horizontal locomotion of mussels was reduced in 100-lx light. Upward movement, exhibited normally by small mussels in darkness, was reduced by light of intensity ≥12 lx. Finally, the percentage of time spent by large mussels with open valves was shorter in dim light (3 and 6 lx) than in darkness. Furthermore, illuminated individuals closed and opened their valves more often than darkened ones. Both these reactions disappeared in strong light (100 lx). In the field, the light-related behaviour of mussels, observed here, might lead to selecting deeper and sheltered sites, which are better protected against predators and dislodgement.

Monitoring environmental habitat of short necked clam at the artificial pocket beach

Wire tagged short necked clams (Ruditapes philippinarum) were released to the artificial pocket beach to evaluate possibility of providing a habitat for the clam, in which maycreate an amusement site for clam-gathering. 1000 tagged clams were released to the site by spreading the dams directly to the sand beach where was surrounded by concrete blocks and by placing the dams into net cases. The tagged dams increased an average 3.4mm of shell length after 49 days. However, the tagged dams which were released directly to the sand beach were killed and fed by moon shells, and the recaptured number was zero after 199 days. The artificial beach can provide an event of dam-gathering where the dams are spread occasionally by human work. Low possibility of creating a sustainable habitat for the clams in this pocket beach is considered.

JAPANESE ABALONE CULTURE PRACTICES AND ESTIMATED COSTS OF JUVENILE PRODUCTION IN THE USA

ABSTRACTApproximately 100 species of abalone are known to exist in the world and commercial abalone fisheries have been established in at least 6 countries. In Japan, 5 species of abalone provide an annual catch of 5,000 metric tons (whole weight with shell) which sells for 6,000/kg (US$27/kg). To increase productivity of coastal waters, juvenile abalone “seed” (10–30 mm) are produced at government operated Fish Farming Centers. Production has increased from 200,000 seed in 1970 to more than 10.7 million in 1978. Survival of artificially reared abalone from larvae to 20 mm averages 1%. Problems still exist in providing the quality and quantity of food required by postlarvae and older juvenile abalone. Twenty millimeter seed is sold by the farming centers to fishermen at a price of $0.10‐0.12 each, which represents only 1/2 to 1/4 of the production costs. Seed is placed in coastal waters for grow‐out to 11–12 cm in 3–5 years. Recapture rates may exceed 10%. Production costs at the only private abalone hatchery in Japan are estimated to be $0.018/mm of shell length. Based on Japanese methods for seed production, an assessment of production costs for an abalone hatchery in the USA is presented. With an annual production of one million abalone (20 mm each) the production cost is estimated to be $0.022/mm of shell length or $0.44/20 mm abalone. The success of abalone production in the USA will be determined by cost effective hatcheries and a strong market for the abalone produced.

The growth of Haliotis tuberculata: results of tagging experiments in Guernsey 1963–65

A tagging investigation on the ormer (Haliotis tuberculata L.) has been carried out for the Guernsey States Sea Fisheries Committee. Cementing plastic discs to the shell has proved a satisfactory technique since substantial numbers of 40—50% were recovered after 1 and 2 years in the open sea off the west coast of Guernsey. From the increase in shell size of the recovered specimens the mean growth rate has been shown to be about 15 mm of shell length per year up to a shell size of 50 mm, and thereafter decreasing until at 100 mm length growth is negligible. The growth parameters K and L∞ have been calculated. Annual rings were frequently, though not invariably, found on the shell. From the frequencies of the shell-ring lengths in the smaller ormers estimates of the shell size reached 1 and 2 years after settlement have been made. A single annual ring was also found with the majority of the larger shells (&gt; 50 mm), though when growth did not exceed 4 mm in a year the rings were not included owing to the difficulty of separating annual rings from possible disturbance rings caused by the process of tagging. The position of the annual ring varied, being closer to the outer edge of the shell with increasing size. Measurements of the length increase from one annual ring to the next indicated rates of growth closely comparable to those obtained from tagging measurements. Damage to the shells by the boring sponge Cliona lobata Hancock is very widespread, particularly in the larger ormers living below the tide marks.