Factors Influencing Egg Extrusion in the American Lobster (Homarus americanus)

1988 ◽  
Vol 45 (5) ◽  
pp. 797-804 ◽  
Author(s):  
K. Nelson ◽  
D. Hedgecock ◽  
W. Borgeson
Keyword(s):  
Adult Female ◽  
Homarus Americanus ◽  
American Lobster ◽  
Molt Cycle ◽  
Young Females ◽  
Factors Influencing ◽  
Long Day ◽  
Alternative Hypotheses

American lobster (Homarus americanus) females characteristically extrude eggs in the summer of the year following a summer or autumn molt, but young females may extrude in the same year. Adult female lobsters were exposed to periods of 40, 80, or 120 d of short photophase (8 h light: 16 h dark) at different times during the molt cycle or as controls were kept under continuous long-day conditions (16 h light: 8 h dark). They were found to require 80 d of short photophase to complete primary vitellogenesis; they then completed secondary vitellogenesis and extruded following long day onset (LDO) only if the latter fell within ± 1400 dd6 (day-degrees above 6 °C) of the molt. The dependence of this latter relationship upon prior delayed extrusion and molting suggests that the decay in probability of LDO-elicited extrusion following the molt proceeds independently of the advance of the current molt cycle. The hypothesis is therefore rejected that the decay in extrusion potential following the molt is a result of increasing probability of interference from the oncoming premolt. Alternative hypotheses are discussed.

Effects of Reproduction upon Molting and Growth in Female American Lobsters (Homarus americanus)

1988 ◽  
Vol 45 (5) ◽  
pp. 805-821 ◽  
Author(s):  
K. Nelson ◽  
D. Hedgecock ◽  
W. Borgeson
Keyword(s):  
Growth Rates ◽  
Homarus Americanus ◽  
Control Group ◽  
American Lobster ◽  
Cycle Duration ◽  
Female Size ◽  
Molt Cycle ◽  
Young Females ◽  
Long Day ◽  
Short Days

American lobster (Homarus americanus) females characteristically extrude eggs (E) in the summer of the year following a summer or autumn molt (M), but young females may extrude in the same year. The subsequent M is delayed until after hatching, resulting in the former case in a 2-yr reproductive molt cycle, measuring from M to M. Adult female lobsters were exposed to periods of short days (8 h light: 16 h dark) followed by long day onset (L) (16 h light: 8 h dark) at different times with respect to M, or as controls were kept under continuous long-day conditions. In this way were generated molt cycles with delayed or undelayed extrusions, as well as ones with incomplete vitellogeneses resulting from too-long delayed L, and molt cycles in which vitrellogenesis did not begin (control group). Delayed L results in delayed E and M, as measured either in days or in day-degrees above 6 °C. An incompleted vitellogenesis following a too-long delayed L changes neither the duration of the molt cycle nor its characteristic positive correlation with female size; the duration of molt cycles containing either delayed or undelayed E appears in contrast to become independent of size. Intermolt intervals following prior E are shorter than those following anovulatory cycles. Retention of the clutch to hatching is associated with an additional increment to the intermolt interval. The results suggest that following E, a "reproductive" program replaces the "somatic" program of control of molt cycle duration. Incompleted vitellogeneses are associated with significantly smaller molt increments and growth rates than in the evidently avitellogenic continuous long-day control group, even though intermolt duration and its relation to size remain the same. Growth rates of molt cycles containing incompleted vitellogeneses are significantly higher than ones containing E only if that is delayed. Differential dependence of molt cycle duration and growth rate measures upon size and temperature indicate that molting and growth are distinct and rather independently controlled processes in adult lobsters, however tightly linked they may be in juveniles. Implications for molting and reproduction in the natural environment are discussed.

Determinants of Postmolt Size in the American Lobster (Homarus americanus). I. D13 is the Critical Stage

1993 ◽  
Vol 50 (10) ◽  
pp. 2106-2111 ◽  
Author(s):  
Jin-Hua Cheng ◽  
Ernest S. Chang
Keyword(s):  
Limb Regeneration ◽  
Homarus Americanus ◽  
American Lobster ◽  
Molt Cycle ◽  
Promoting Effect ◽  
Critical Stage ◽  
Eyestalk Ablation ◽  
Growth Promoting ◽  
Large Container

Juvenile American lobster (Homarus americanus) were subjected to induced limb autotomy, eyestalk ablation, and manipulation of container space at different molt stages to test the hypothesis that postmolt size is predetermined at the time of deposition of the epicuticle. Molt increments in autotomized animals that regenerated limbs were reduced by 30–40%. Molt increments were reduced by only 5–10% in autotomized animals that did not regenerate limbs. The critical stage for limb regeneration is D13. Depending on the time of limb autotomy, molt intervals were decreased (stages B–C), increased (stages D11 and D12), or not affected (stages D0, D13, D2, and D3). Eyestalk ablation shortened the molt interval; the change in molt interval was less when ablation was performed near the end of the current molt cycle. Eyestalk-ablated lobsters had larger molt increments compared with intact controls, especially in the chelipeds. This growth-promoting effect disappeared if ablation was conducted at or after D13. Transferring lobsters from small to large container spaces shortened molt intervals and increased molt increments. Increases in molt increments only occurred when transfers were made before D13. We conclude that postmolt size of lobsters is predetermined at D13 when the new epicuticle is produced.

Oocyte Maturation and Spawning in Wild American Lobsters (Homarus americanus): Lack of Evidence for Significant Regulation by Photoperiod

1986 ◽  
Vol 43 (7) ◽  
pp. 1451-1453 ◽  
Author(s):  
D. E. Aiken ◽  
S. L. Waddy
Keyword(s):  
Oocyte Maturation ◽  
East Coast ◽  
Homarus Americanus ◽  
Mature Female ◽  
American Lobster ◽  
Ovarian Maturation ◽  
Long Day ◽  
Autumnal Equinox ◽  
Spawning Time ◽  
Short Days

The literature indicates that spawning in the American lobster (Homarus americanus) requires exposure to short days followed by long days, but our previous experiments with mature female lobsters showed no such requirement. To reevaluate the reported photoperiod requirement and to determine whether a photoperiod stimulus for ovarian maturation might occur well before the current spawning season, we held wild-caught mature Gulf of St. Lawrence females on either long (LD 16:8) or short (LD 1:23) days starting at the autumnal equinox. Females held on both short and long days spawned at the normal time the following July, indicating no effect of photoperiod even 10 mo before normal spawning time. This study extends previous work by showing that Gulf of St. Lawrence lobsters held on typical East Coast seawater temperatures will spawn at the normal time without being exposed to either short-day or long-day photoperiod between 22 September and the following July.

Growth of juvenile American lobster Homarus americanus in a changing environment

2016 ◽  
Vol 557 ◽  
pp. 177-187 ◽  
Author(s):  
MD McMahan ◽  
DF Cowan ◽  
Y Chen ◽  
GD Sherwood ◽  
JH Grabowski
Keyword(s):  
Homarus Americanus ◽  
American Lobster ◽  
Changing Environment

Predicting bycatch hotspots based on suitable habitat derived from fishery-independent data

2020 ◽  
Vol 641 ◽  
pp. 159-175
Author(s):  
J Runnebaum ◽  
KR Tanaka ◽  
L Guan ◽  
J Cao ◽  
L O’Brien ◽  
...  
Keyword(s):  
Habitat Suitability ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Gulf Of Maine ◽  
Homarus Americanus ◽  
Management Tool ◽  
American Lobster ◽  
Suitable Habitat ◽  
Climate Conditions ◽  
Suitability Index

Bycatch remains a global problem in managing sustainable fisheries. A critical aspect of management is understanding the timing and spatial extent of bycatch. Fisheries management often relies on observed bycatch data, which are not always available due to a lack of reporting or observer coverage. Alternatively, analyzing the overlap in suitable habitat for the target and non-target species can provide a spatial management tool to understand where bycatch interactions are likely to occur. Potential bycatch hotspots based on suitable habitat were predicted for cusk Brosme brosme incidentally caught in the Gulf of Maine American lobster Homarus americanus fishery. Data from multiple fisheries-independent surveys were combined in a delta-generalized linear mixed model to generate spatially explicit density estimates for use in an independent habitat suitability index. The habitat suitability indices for American lobster and cusk were then compared to predict potential bycatch hotspot locations. Suitable habitat for American lobster has increased between 1980 and 2013 while suitable habitat for cusk decreased throughout most of the Gulf of Maine, except for Georges Basin and the Great South Channel. The proportion of overlap in suitable habitat varied interannually but decreased slightly in the spring and remained relatively stable in the fall over the time series. As Gulf of Maine temperatures continue to increase, the interactions between American lobster and cusk are predicted to decline as cusk habitat continues to constrict. This framework can contribute to fisheries managers’ understanding of changes in habitat overlap as climate conditions continue to change and alter where bycatch interactions could occur.

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