Delayed Recruitment Models and Their Application to the American Lobster (Homarus americanus) Fishery

A delayed recruitment model intended for use in developing dynamic strategies for fisheries management is proposed. The conceptual and analytical properties of the model are elaborated and compared with those of the instantaneous model of Schaefer and the delayed recruitment model recently suggested by Walter. Of the three models discussed, the delayed recruitment model proposed herein constitutes the more biologically meaningful tool for use in management decision making with fisheries characterized by a multiple year delay between spawning and recruitment. The proposed delay and Schaefer models are fitted to catch and effort data from the Rhode Island inshore pot lobster fishery, and the generated coefficients are examined with respect to their interpretation and relative importance. Values of optimum equilibrium catch and effort are calculated for the proposed delay and Schaefer models, and we show that the delay model’s estimates of these management indices are more conservative than those derived from Schaefer’s model. The proposed delay and Schaefer models are compared in a dynamic analysis of the fishery, in which perturbations in the stock level and fluctuations in the applied effort are simulated to predict the subsequent behavior of the stock.

Download Full-text

American lobster nurseries of southern New England receding in the face of climate change

ICES Journal of Marine Science ◽

10.1093/icesjms/fsv093 ◽

2015 ◽

Vol 72 (suppl_1) ◽

pp. i69-i78 ◽

Cited By ~ 30

Author(s):

Richard A. Wahle ◽

Lanny Dellinger ◽

Scott Olszewski ◽

Phoebe Jekielek

Keyword(s):

New England ◽

Rhode Island ◽

Size Composition ◽

Homarus Americanus ◽

Warming Trend ◽

Shore Crab ◽

American Lobster ◽

Southern New England ◽

Study Sites ◽

Outer Coast

Abstract Historically, southern New England has supported one of the most productive American lobster (Homarus americanus) fisheries of the northeast United States. Recently, the region has seen dramatic declines in lobster populations coincident with a trend of increasingly stressful summer warmth and shell disease. We report significant declines in the abundance, distribution, and size composition of juvenile lobsters that have accompanied the warming trend in Narragansett Bay, Rhode Island, since the first comprehensive survey of lobster nurseries conducted there in 1990. We used diver-based visual surveys and suction sampling in 1990, 2011, and 2012, supplemented by post-larval collectors in 2011 and 2012. In 1990, lobster nurseries extended from the outer coast into the mid-sections of the bay, but by 2011 and 2012 they were largely restricted to the outer coast and deeper water at the mouth of the bay. Among five new study sites selected by the lobster fishing industry for the 2011 and 2012 surveys, the deepest site on the outer coast (15–17 m depth) harboured some of the highest lobster densities in the survey. Separate fixed site hydrographic monitoring at 13 locations in the bay by the Rhode Island Division of Fish and Wildlife recorded an approximately 2.0°C increase in summer surface temperatures over the period, with 2012 being the warmest on record. Additional monitoring of bottom temperatures, dissolved oxygen and pH at our sampling sites in 2011 and 2012 indicated conditions falling below physiological optima for lobsters during summer. The invasion of the Asian shore crab, Hemigrapsus sanguineus, since the 1990s may also be contributing to declines of juvenile lobster shallow zones (<5 m) in this region. Because lobster populations appear increasingly restricted to deeper and outer coastal waters of southern New England, further monitoring of settlement and nursery habitat in deep water is warranted.

Download Full-text

A simulation study to evaluate impacts of uncertainty on the assessment of American lobster fishery in the Gulf of Maine

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f02-102 ◽

2002 ◽

Vol 59 (8) ◽

pp. 1394-1403 ◽

Cited By ~ 19

Author(s):

Yong Chen ◽

Carl Wilson

Keyword(s):

Confidence Level ◽

Gulf Of Maine ◽

Homarus Americanus ◽

American Lobster ◽

Large Uncertainty ◽

Decision Confidence ◽

The Status ◽

Status Assessment ◽

Lobster Fishery ◽

Risk Managers

The status of the American lobster (Homarus americanus) in the Gulf of Maine (GOM) has been assessed for the last two decades by comparing an estimated current fishing mortality rate for females (Fcur) with a deterministically estimated biological reference point, F10%. The most recent assessment determined that GOM had exceeded the F10% for every year calculated, although in this time landings and abundance have doubled. The current policy does not consider uncertainty in the assessment. This study evaluates the impacts of uncertainty in F10% and Fcur on the status assessment of lobster fishery. Using a Monte Carlo simulation approach, we found that the status assessment would be influenced by uncertainties in estimating F10% and Fcur, and by the choice of decision confidence level reflecting the level of risk managers would like to take. A large uncertainty in Fcur and F10% and a high decision confidence level reduce the likelihood of defining the stock as overfished, and vice versa. Our results suggest that the probability of lobster overfishing may be less than previously thought, and that uncertainty in Fcur and F10% should be quantified and considered in determining the status of the GOM lobster stock.

Download Full-text

Quantitative relationships between postlarval production and benthic recruitment in lobsters, Homarus americanus

Marine and Freshwater Research ◽

10.1071/mf97204 ◽

1997 ◽

Vol 48 (8) ◽

pp. 729 ◽

Cited By ~ 30

Author(s):

Lewis S. Incze ◽

Richard A. Wahle ◽

J. Stanley Cobb

Keyword(s):

Rhode Island ◽

Annual Variation ◽

Gulf Of Maine ◽

Homarus Americanus ◽

Seasonal Abundance ◽

Moult Cycle ◽

American Lobster ◽

Temperature Dependent ◽

Dependent Growth ◽

Island Sound

Relationships between lobster postlarval supply and benthic recruitment were evaluated within and between oceanographically distinct segments of the range of the American lobster. Postlarvae (PL) were sampled by neuston nets in western Rhode Island Sound and the western Gulf of Maine, USA, from June to September 1989–95. Benthic lobsters were sampled in sublittoral cobble habitat by using a diver-operated airlift at the end of the settlement season. Average annual recruitment densities of young-of-year (YOY) lobsters ranged from 0.3 to 1.7 m-2. YOY recruitment was positively correlated between areas. Integrated seasonal abundance of postlarvae was often much greater in Rhode Island than Maine, but production estimates (PL 1000 m-2 season-1), calculated from moult cycle stages and temperature-dependent growth rates, differed by a factor of <0.5. PL production was positively correlated between areas and explained ≥81% of the annual variation in recruitment in each area and 90% for the two areas combined. In Maine, among-site differences in YOY recruitment persisted for a year after settlement and then began to lessen, at least in part because larger individuals moved into areas of initially lower recruitment

Download Full-text

Applications of Biochemical Genetics to Aquaculture

Journal of the Fisheries Research Board of Canada ◽

10.1139/f76-139 ◽

1976 ◽

Vol 33 (4) ◽

pp. 1108-1119 ◽

Cited By ~ 27

Author(s):

Dennis Hedgecock ◽

Robert A. Shleser ◽

Keith Nelson

Keyword(s):

Gel Electrophoresis ◽

Biochemical Analysis ◽

Natural Populations ◽

Homarus Americanus ◽

Larval Survival ◽

Mendelian Inheritance ◽

Hybrid Vigor ◽

American Lobster ◽

Biochemical Genetics ◽

Lobster Fishery

American lobster (Homarus americanus) catches are diminishing. More than 90% of the annual catch is 2.2-kg (1-lb) minimum legal size. Females of this size may have produced 10,000 eggs prior to catch, but, with an estimated larval survival of 1/100,000, 10 females are required to reproduce 1 female. The prognosis for the lobster fishery appears poor.Laboratory culture of larval lobsters can achieve more than 60% survival at a cost of about 2¢ per postlarval juvenile. The effectiveness of restocking has never been evaluated.Starch-gel electrophoresis reveals protein differences among individual lobsters: progeny studies confirm Mendelian inheritance of allozymes encoded by five independent genes, Est-2, Idh, Pgi-3, Pgi-4, and Pgm-1. Genetic markers may be determined by biochemical analysis of pereiopod tissue, without killing. Allozyme frequencies have been measured in natural populations (e.g. Pgm-1103 is absent in lobsters from Martha’s Vineyard (MVS), but occurs elsewhere in frequencies of 0.C2). Larvae with rare allozyme genotypes (e.g. Pgm-1100/103 or Pgm-1103/103 at MVS) may be obtained from selected females or produced by appropriate matings. These may be released, and their survival at selected times after release monitored by leg sampling from lobsters of the appropriate age-class. This technique is being used to select diverse parental stocks and produce progeny which may show hybrid vigor. These stocks will be used in developing lobster farming.

Download Full-text

The Effect of a Change in the Size at First Capture in the Rhode Island Inshore Lobster Fishery: A Bioeconomic Analysis

Journal of the Northeastern Agricultural Economics Council ◽

10.1017/s0163548400003939 ◽

1983 ◽

Vol 12 (2) ◽

pp. 121-121

Author(s):

Edward J. Richardson

Keyword(s):

Rhode Island ◽

Homarus Americanus ◽

Minimum Size ◽

Full Time ◽

Fleet Size ◽

Regional Market ◽

Length Increase ◽

Short Run ◽

Lobster Fishery ◽

Social Surplus

At this time minimum size limit regulations are the primary tool used to manage Rhode Island's American lobster (Homarus americanus) resource. One shortcoming of this policy is its lack of foundation in bioeconomic analysis. To encourage the incorporation of bioeconomic considerations into the management strategy used on this valuable resource, a fishery simulator (Gates 1974) was modified and employed to analyze the effects of changing the size at first capture in Rhode Island's inshore lobster fishery.A cost and earnings survey of Rhode Island's commercial lobster license holders was conducted to provide the economic data required to simulate the fishery. This survey uncovered information characterizing the exploitation of the resource. For example, the survey estimated inshore catch of 2.1 million pounds indicates that three quarters of the inshore catch may go unrecorded. The survey also revealed that full-time commercial harvesters are outnumbered by part-time personnel by a factor of seven, but still land over 90% of Rhode Island's lobster catch.The simulation results also proved quite informative. They suggest that an increase in Rhode Island's minimum size at first capture, if promulgated alone, will not confer increased benefits to society or fishermen. In fact, if a reasonable rate of discount is employed, the analysis indicates the measure will decrease the present value of social surplus generated by Rhode Island's inshore lobster fishery. Averaging over the range of results obtained, an 0.8 mm carapace length increase will reduce annualized benefits by 7%. Alternative larger increases of 1.6 mm and 9.5 mm (3.5 inch minimum) are estimated to bring about 10% and 38% reductions in the annualized value of social surplus that the inshore fishery can be expected to generate. These results are due in part to the substantial short run decreases in catch that the increased minimum sizes generate, and in part because it is assumed that the increased minimum size will govern Rhode Island's landings only.The immediate short run decreases in benefits that accompany the minimum size increases were found to fall primarily on the harvesters of the resource. Averaging over the discount rates employed, 87% of the short run reductions in social surplus subtracted from producer revenues. All results assume that stock recruitment is independent of stock size, that stock reproductive security is not at issue, and that lobster prices are determined in a regional market for live lobsters.Additional simulations were performed to compare the social surplus in the open access fishery with that which might be obtained should access to the fishery be restricted. Also, social surpluses were obtained for the fishery under the assumption that an increased size at first capture results in increased recruitment. These simulations point to the general result that increased harvest selectivity will maximize the sustainable fleet size while concurrently reducing the annual social surplus generated by the fishery.

Download Full-text

Centralization and Effectiveness of Reward Management in Multinational Enterprises

Journal of Personnel Psychology ◽

10.1027/1866-5888/a000195 ◽

2018 ◽

Vol 17 (2) ◽

pp. 55-65 ◽

Cited By ~ 1

Author(s):

Michael Tekieli ◽

Marion Festing ◽

Xavier Baeten

Keyword(s):

Decision Making ◽

Social Identity Theory ◽

Multinational Enterprises ◽

Role Identity ◽

Management Decision ◽

Role Identities ◽

Management Decision Making ◽

New Perspective ◽

Subsidiary Managers ◽

The Relationship

Abstract. Based on responses from 158 reward managers located at the headquarters or subsidiaries of multinational enterprises, the present study examines the relationship between the centralization of reward management decision making and its perceived effectiveness in multinational enterprises. Our results show that headquarters managers perceive a centralized approach as being more effective, while for subsidiary managers this relationship is moderated by the manager’s role identity. Referring to social identity theory, the present study enriches the standardization versus localization debate through a new perspective focusing on psychological processes, thereby indicating the importance of in-group favoritism in headquarters and the influence of subsidiary managers’ role identities on reward management decision making.

Download Full-text