Size–Maturity Relationships and Related Observations in Newfoundland Populations of the Lobster (Homarus americanus)

1980 ◽  
Vol 37 (6) ◽  
pp. 945-956 ◽  
Author(s):  
G. P. Ennis
Keyword(s):  
Carapace Length ◽  
Size Range ◽  
Sex Ratios ◽  
Weight Ratio ◽  
Homarus Americanus ◽  
Spawning Season ◽  
Length Ratio ◽  
Maturity Indices

Female maturity ogives for five Newfoundland populations of the lobster (Homarus americanus) gave 50% maturities ranging from 71- to 76-mm carapace length. Sizes at which distinct inflections (indicating onset of maturity) and asymptotes (indicating 100% mature) are present in the abdomen width/carapace length ratio vs. carapace length relationships coincide with the smallest ovigerous and largest immature specimens, respectively, observed in those particular samples. Inflection in the crusher claw weight/whole weight ratio vs. carapace length relationships (used in this paper to indicate onset of maturity in males) occurred at larger sizes than inflections in the abdomen width/carapace length ratios of females.The percentage of nonovigerous females that spawn in a given year generally increases with increasing size. The highest percentage of nonovigerous females tagged with sphyrion tags prior to the spawning season that were ovigerous when recaptured 10–12 mo later was 83.8%. The percentage of ovigerous females with new shells (i.e. molted and spawned in same year) varied between areas and years and ranged from 0 to 38.5% of the total number of ovigerous females in fall samples. The percentage of ovigerous females in samples also varied between areas and years and ranged from 2.6 to 30.4% of the total number of females greater than the size at 50% maturity. In general a greater percentage of females was ovigerous at sizes between the size at 50% maturity and 80 mm (largest subcommercial size) than at commercial sizes.In a sample of nonovigerous females, the size range at which 50% were fertilized (76–80 mm) coincided closely with the size at 50% maturity (75 mm) for the area.At subcommercial sizes (< 81 mm) the sexes were approximately equally represented in fall trap-caught samples but females heavily outnumbered males in diver-caught samples taken over the same period. At commercial sizes, however, males heavily outnumbered females in the trap-caught samples while in diver-caught samples the sexes were equally represented.Key words: lobster (Homarus americanus), maturity ogives, maturity indices, percent ovigerous, sex ratios

The catchability of large American lobsters (Homarus americanus) from diving and trapping studies off Grand Manan Island, Canadian Maritimes

2006 ◽  
Vol 63 (9) ◽  
pp. 1925-1933 ◽  
Author(s):  
M J Tremblay ◽  
S J Smith ◽  
D A Robichaud ◽  
P Lawton
Keyword(s):  
Generalized Linear Models ◽  
Carapace Length ◽  
Linear Models ◽  
Size Range ◽  
Late Summer ◽  
Homarus Americanus ◽  
Agonistic Interactions ◽  
Size Groups ◽  
Early Fall ◽  
Catch Rates

Catchability (q) in traps was estimated for American lobsters (Homarus americanus) in Flagg Cove, off Grand Manan Island (New Brunswick, Canada), where large females (>100 mm carapace length (CL)) aggregate in late summer and early fall. In 2001 and 2002, diver surveys were used to estimate lobster density, and traps were then deployed to obtain catch rates. Bayesian generalized linear models were fit to the densities of different size groups (81–100, 101–130, 131–160, and >160 mm CL) of ovigerous females, non-ovigerous females, and males. Catchability was strongly affected by year. Differences in q due to sex and size for ovigerous females, non-ovigerous females, and males were apparent but were not consistent between years. Size was not an important factor for the catchability of lobsters between 81 and 160 mm CL. In comparison with lobsters of a similar size in other areas, Flagg Cove lobsters in the size range of 81–100 mm CL were less catchable. We hypothesize that this resulted from the high densities and larger sizes of lobsters in Flagg Cove, which likely lead to increased agonistic interactions and reduced entry of lobsters into traps.

Growth Per Moult of Tagged Lobsters (Homarus americanus) in Bonavista Bay, Newfoundland

1972 ◽  
Vol 29 (2) ◽  
pp. 143-148 ◽  
Author(s):  
G. P. Ennis
Keyword(s):  
Carapace Length ◽  
Size Range ◽  
Homarus Americanus ◽  
Total Weight ◽  
Growth Studies ◽  
Field Samples ◽  
Length Increment ◽  
Significant Change

The suitability of the sphyrion tag for lobster growth studies is demonstrated by comparing growth of ferromagnetic- and sphyrion-tagged lobsters. Carapace length and total weight increments in one moult of 54 males (52–92-mm carapace length) tagged with sphyrion tags averaged 11.4 mm (15.7%) and 185.9 g (60.8%). For 56 females 57–89-mm carapace length they averaged 9.8 mm (13.3%) and 136.3 g (42.5%). Differences in growth per moult between sexes increased with size. For both sexes percent carapace length increment decreased with increase in carapace length but more rapidly for females. Carapace length increment increased with increasing carapace length for males, but for females there was no significant change over the size range considered. Incidence of moulting for sphyrion-tagged lobsters was 83.1% and comparable with an observed estimate (85.2%) from field samples obtained shortly after the moulting season.

Multiple Fertilization and Consecutive Spawning in Large American Lobsters, Homarus americanus

1986 ◽  
Vol 43 (11) ◽  
pp. 2291-2294 ◽  
Author(s):  
S. L. Waddy ◽  
D. E. Aiken
Keyword(s):  
Body Size ◽  
Carapace Length ◽  
Homarus Americanus ◽  
Large Female ◽  
Bay Of Fundy ◽  
Relative Fecundity ◽  
Logarithmic Relationship

Large female American lobsters, Homarus americanus (> 120 mm carapace length), maintained at nearshore Bay of Fundy temperatures often spawn twice without an intervening molt (consecutive spawning). Consecutive spawning occurs in two forms: successive-year (spawning in two successive summers, a molt in the first and fourth years) and alternate-year (spawning in alternate summers, a molt in the first and fifth years). In both types, females often are able to fertilize the two successive broods with the sperm from a single insemination (multiple fertilization). Twenty of 21 large females that were held for up to 13 yr displayed one of these types of consecutive spawning. Consecutive spawning and multiple fertilization enable large lobsters to spawn more frequently over the long term than their smaller counterparts. This, combined with the logarithmic relationship between body size and numbers of eggs produced, means that very large lobsters have a much greater relative fecundity than previously thought.

Peanut yield and quality variation over harvest dates, and evaluation of some maturity indices in south-eastern Queensland

1987 ◽  
Vol 27 (3) ◽  
pp. 445 ◽  
Author(s):  
R Shorter ◽  
BW Simpson
Keyword(s):  
Weight Ratio ◽  
Kernel Weight ◽  
South Eastern ◽  
Yield And Quality ◽  
Harvest Dates ◽  
Maturity Indices ◽  
Arachis Hypogaea L ◽  
Crop Development ◽  
Moisture Percentage ◽  
Kernel Yield

Yield and quality variations across harvest dates in peanuts (Arachis hypogaea L.) grown under rainfed conditions in south-eastern Queensland in 1978-79 and 1980-81 were investigated. Free arginine percentage of kernels, kernel: hull weight ratio, shell-out percentage, mean individual kernel weight and kernel moisture percentage were monitored during crop development to assess their usefulness as indices of crop maturity. For the Virginia Bunch cultivar, kernel yield ranged from 1862 kg ha-1 at 133 days after sowing (DAS) to 2432 kg ha-l at 168 DAS in 1978-79 and from 687 kg ha-l at 201 DAS to 1618 kg ha-1 at 152 DAS in 1980-81. In both years kernel yield and crop value for Virginia Bunch exhibited bimodal responses to delayed harvesting, with maximum values being obtained at about 150 and 170 DAS. These responses tended to be associated with rainfall distribution and available soil moisture during flowering. None of the maturity indices investigated was sensitive enough to detect the 2 peaks for yield or crop value and therefore would be of no use in determining optimum harvest periods for Virginia Bunch. Red Spanish and White Spanish cultivars, evaluated in 1978-79, produced average kernel yields of 1777 kg ha-l and 1535 kg ha-1 respectively. For these cultivars, differences in yield and crop value over harvest dates were not significant. Although kernel yields did not increase after 133 DAS, the decline in free arginine percentage and the increase in the kerne1:hull weight ratio during the season suggested that these indices may be useful indicators of optimum maturity for spanish-type cultivars.

Morphological maturity and allometric growth in the squat lobster Munida rugosa

2009 ◽  
Vol 89 (6) ◽  
pp. 1189-1194 ◽  
Author(s):  
Thomas Claverie ◽  
I. Philip Smith
Keyword(s):  
Measurement Error ◽  
Sexual Maturity ◽  
Carapace Length ◽  
Size Range ◽  
Size At Maturity ◽  
Allometric Growth ◽  
Positive Allometry ◽  
Squat Lobster

Size at the onset of sexual maturity was determined in Munida rugosa based on allometric growth of chelipeds and abdomen, and on the proportion of ovigerous females. The variability of three different measurements of carapace length (CL) used previously for M. rugosa was also evaluated to minimize measurement error. Both sexes had symmetrical cheliped length and allometric cheliped growth over the size-range investigated, but males showed increased allometry beyond 22 mm CL. Females had greater positive allometry in abdomen width than males, but their size at maturity could not be precisely determined because sampled females were too large.

Laboratory and Field Tests of Modified Sphyrion Tags on Lobsters (Homarus americanus)

1970 ◽  
Vol 27 (2) ◽  
pp. 257-264 ◽  
Author(s):  
D. J. Scarratt
Keyword(s):  
Carapace Length ◽  
Field Tests ◽  
Homarus Americanus ◽  
Poor Survival ◽  
Internal Organs ◽  
Fishing Season ◽  
Tag Loss

Mortalities of lobsters held in the laboratory and tagged with sphyrion tags inserted dorsally between the carapace and abdomen (subcarapace tag) and between the second and third abdominal segments (abdomen tag) did not differ significantly. Premoult tag loss was negligible. The subcarapace tag was retained significantly better through moulting.Returns of subcarapace-tagged and abdomen-tagged lobsters released on the fishing grounds in June, 11 weeks before the August 10 opening of the fishing season, were lower than returns of carapace-tagged lobsters released in early August. More subcarapace-tagged than abdomen-tagged lobsters were returned, and a higher proportion had moulted. Growth was comparable to that reported in the literature. Few lobsters were recaptured during the following fishing season, 14–16 months after liberation, and none subsequently. Returns from lobsters less than 63.5 mm carapace length (sublegal) when tagged were extremely low. Poor survival may be related in part to time of release. Some injury to internal organs may occur with both tags. The subcarapace tag is clearly superior but may be of limited value in the field for lobsters below 63.5 mm carapace length.

Biennial Reproductive Cycle of Blue King Crab, Paralithodes platypus, at the Pribilof Island, Alaska and Comparison to a Congener, P. camtschatica

1989 ◽  
Vol 46 (6) ◽  
pp. 932-940 ◽  
Author(s):  
Gregory C. Jensen ◽  
David A. Armstrong
Keyword(s):  
Carapace Length ◽  
Reproductive Output ◽  
Size Range ◽  
Egg Mass ◽  
King Crab ◽  
Pribilof Island ◽  
Blue King Crab ◽  
Paralithodes Platypus ◽  
One Year ◽  
Reproductive Events

Pribilof Island blue king crab (BKC; Paralithodes platypus) were sampled by beam trawl in May and August of 1983 and April 1984 to determine timing of reproductive events. Biennial reproduction was found to be the result of slow ovarian growth in large, muciparous females, while smaller primiparous females are often able to spawn in two consecutive years. Mating and egg extrusion occur in late March to early May and eggs hatch in mid-April of the following year, consequently, the embryonic period and rate of development is approximately 12 mo, similar to that of its congener the red king crab (RKC; P. camtschatica). Comparison of the reproductive output of the two species revealed that despite the 2 yr ovarian cycle, BKC only produce 20–30% more dry egg mass at any carapace length than do RKC, a substantially smaller difference than previously calculated. One year after molt, females of both species are not significantly different in dry body weight over a size range of 100–140 mm carapace length, but RKC have produced about three times more dry ovarian weight than BKC of comparable size, suggesting that biennial reproduction in BKC may be the result of energetic limitations.

Biological tags as moult indicators in Panulirus cygnus (George)

1997 ◽  
Vol 48 (8) ◽  
pp. 959 ◽  
Author(s):  
R. Melville-Smith ◽  
J. B. Jones ◽  
R. S. Brown
Keyword(s):  
Carapace Length ◽  
Size Range ◽  
Field Trials ◽  
Size Category ◽  
Fishing Season ◽  
Panulirus Cygnus ◽  
Biological Tags

Laboratory and field trials were employed to examine the feasibility of using biological tags as moult indicators. Twenty-four animals were tagged with epidermal implants and held in aquaria for 2 years and 8 months before the tags were removed. Five tags failed to form useful cysts and one tag was damaged during processing. The remaining 18 lobsters moulted between three and six times, with this moulting record being accurately verified by 15 of the biological tags and incorrectly interpreted (by one moult) in one case. Two tags produced inconclusive results. Biological tags were tested in the field in the Fremantle area, with 132 animals being recaptured out of 1336 tagged. Eleven tags proved impossible to read, eight failed to form cysts, and the balance recorded up to six moults during the release period. Animals in the size range 60–80 mm carapace length (CL) recorded two moults per year, one in February–April and a second before the mid-November start to the fishing season. Females grew significantly less per moult than did males in the same size category (60–85 mm CL), and both sexes showed significantly smaller increments for animals ≥85 mm CL at release.

scholarly journals The Effects of Feature Sizes in Selectively Laser Melted Ti-6Al-4V Parts on the Validity of Optimised Process Parameters

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 117 ◽  
Author(s):  
Chinmay Phutela ◽  
Nesma T. Aboulkhair ◽  
Christopher J. Tuck ◽  
Ian Ashcroft
Keyword(s):  
Mechanical Properties ◽  
Process Parameters ◽  
Size Range ◽  
Weight Ratio ◽  
High Strength ◽  
Major Change ◽  
Technology Readiness ◽  
Feature Size ◽  
Excellent Corrosion Resistance ◽  
Fixed Set

Ti-6Al-4V is a popular alloy due to its high strength-to-weight ratio and excellent corrosion resistance. Many applications of additively manufactured Ti-6Al-4V using selective laser melting (SLM) have reached technology readiness. However, issues linked with metallurgical differences in parts manufactured by conventional processes and SLM persist. Very few studies have focused on relating the process parameters to the macroscopic and microscopic properties of parts with different size features. Therefore, the aim of this study was to investigate the effect of the size of features on the density, hardness, microstructural evolution, and mechanical properties of Ti-6Al-4V parts fabricated using a fixed set of parameters. It was found that there is an acceptable range of sizes that can be produced using a fixed set of parameters. Beyond a specific window, the relative density decreased. Upon decreasing the size of a cuboid from (5 × 5 × 5 mm) to (1 × 1 × 5 mm), porosity increased from 0.3% to 4.8%. Within a suitable size range, the microstructure was not significantly affected by size; however, a major change was observed outside the acceptable size window. The size of features played a significant role in the variation of mechanical properties. Under tensile loading, decreasing the gauge size, the ultimate and yield strengths deteriorated. This investigation, therefore, presents an understanding of the correlation between the feature size and process parameters in terms of the microscopic and macroscopic properties of Ti-6Al-4V parts manufactured using SLM. This study also highlights the fact that any set of optimized process parameters will only be valid within a specific size window.

Intermolt Insemination, an Alternative Mating Strategy for the American Lobster (Homarus americanus)

1990 ◽  
Vol 47 (12) ◽  
pp. 2402-2406 ◽  
Author(s):  
S. L. Waddy ◽  
D. E. Aiken
Keyword(s):  
Reproductive Strategy ◽  
Carapace Length ◽  
Homarus Americanus ◽  
Mating Strategy ◽  
American Lobster ◽  
Male Aggression ◽  
Female Receptivity ◽  
Molt Stage ◽  
Alternative Mating Strategy ◽  
Ovarian Stage

American lobster (Homarus americanus) have a dual mating strategy. Although most females mate when they are newly molted, mating can occur at any molt stage if necessary, in the laboratory, virtually all uninseminated preovigerous females mate prior to spawning. Male aggression is a major factor in the success of intermolt mating and males can discriminate between immature and mature females, and between inseminated and uninseminated females. Female receptivity is affected by both ovarian stage and the presence of stored sperm, but not by molt stage. Most females become unreceptive after insemination, but their receptivity returns once the supply of stored sperm is exhausted. Intermolt mating occurs in smaller lobster that for some reason did not mate at molt, and it is an important part of the reproductive strategy of larger lobster. Lobster s[Formula: see text] carapace length frequently spawn twice without molting and often fail to store sufficient sperm to fertilize consecutive spawnings. Intermolt mating ensures these females will produce fertile second broods.

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