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Welcome!

Welcome to our website. We are the fisheries and ecosystem assessment team from Florida International University. We created this website to introduce our spiny lobster stock assessment project to you. You may not be familiar with stock assessment or spiny lobster: this website will be a good place to explore. 

What is stock assessment?

The assessment of the size and state of the stocks exploited by fisheries is one of the pillars of modern management. Stock assessment scientists collect both biological and fisheries data. These data are applied to develop models to evaluate the stock condition of the species and to predict future trends of stock abundance. Stock assessments provide fisheries managers with the information that is used in the regulation of a fish stock. 

Spiny Lobster

The spiny lobster, Panulirus argus, is a decapod crustacean distributed throughout the subtropical western Atlantic [1]. It is widely distributed in tropical and subtropical waters of the Atlantic Ocean. It has been harvested by 23 counties in the Caribbean area.

The spiny lobster is covered with an exoskeleton. The exoskeleton does not expand, therefore the lobster must molt it regularly in order to grow bigger. Before molting, an individual begins building a new, larger skeleton inside the existing one. As it gets too big to be contained, it splits open the outer shell, and the new exoskeleton hardens [2]. The spiny lobster could grow up to 60 cm (24 in) long, but typically around 20 cm (7.9 in). Sexual maturity in females is reached at a carapace length of 54–80 mm (2.1–3.1 in) [2]. The spiny lobster is benthic. The diet is mostly composed of mollusks, but they also consume detritus, vegetable material, and dead animals and fish they find on the bottom [3]. 

Spiny Lobster Fisheries and Stock Assessment of USA

Most of the US southeastern spiny lobster harvest comes from Florida, mainly the Florida Keys [4]. The annual lobster landings in Florida peaked at more than 10 million pounds in 2001 [5]. However, after 2001, this value decreased substantially. In 2010, the state’s annual lobster landing was around 5.5 million pounds; about 50% of what it was 10 years earlier [6].

Commercial spiny lobster fisheries use traps to catch the lobsters, while recreational anglers harvest spiny lobsters primarily by diving.

The stock condition of the spiny lobster in the southeast US was assessed by the Florida Fish and Wildlife Conservation Commission (FWC), under the supervision of Southeast Data, Assessment, and Review (SEDAR). The latest stock assessment was conducted at the end of 2010, when an integrated Catch-at-Age Model and a Modified DeLury Model were applied. The results of those two models have been peer-reviewed by an independently selected panel. The Review Panel rejected the report and identified three concerns about the methods: 1) uncertainty in estimating juvenile natural mortality because of the Panulirus argus virus 1 (PaV1); 2) limited knowledge of the stock-recruitment relationship because of the external recruitment from upstream Caribbean stocks; 3) inaccurate and imprecise estimation of the age composition [6]. 

 

 

Spiny lobster under the shelter.

Commercial spiny lobster trap.

Photo Credit: John Plotkin 

Recreational diver harvests lobsters.

Photo Credit: Scuba Diving.com

Objective

The main objective of this project is to develop a size-structured model to better assess the status of the spiny lobster stock in the southeast US. To achieve this objective, 8 steps need to be completed:

 

  • Design and develop submodels to simulate the lobster life history and fisheries processes;

  • Identify statistical estimators for the stock assessment model;

  • Develop an Individual based model to generate a growth transition matrix for the stock assessment model;

  • Collect fisheries-dependent data for the stock assessment model;

  • Develop and debug the stock assessment model by using Bayesian framework;

  • Use the models to estimate the status of the spiny lobster fishery and to develop biological reference points;

  • Discuss the preliminary results with Florida FWC fisheries scientists, and fine-tune the model;

  • Provide the size-structured stock assessment model and the individual-based model (IBM) to end-users for future stock assessments.

Reference: 

[1] Herrnkind, WQ. F., and M. Bulter IV. 1986. Factors regulating postlarval settlement and juvenile microhabitat use by spiny lobsters Panulirus argus. Mar. Ecol. 34: 23–30.

[2] http://oceana.org/en/explore/marine-wildlife/caribbean-spiny-lobster

[3] J. L. Munro (1983). "The biology, ecology and bionomics of spiny lobsters (Palinuridae), apider crabs (Majidae) and other crustacean resources". In J. L. Munro. Caribbean Coral Reef Fishery Resources. ICLARM Technical Reports 7 (2nd ed.). The WorldFish Center. pp. 206–222. ISBN 978-971-10-2201-3.

[4] Prochaska, F. J., & Williams, J. S. (1978). An Economic Analysis of Spiny Lobster Production by Individual Firms at Optimum Stock Levels. Southern Journal of Agricultural Economics, 10(02).

[5] Sharp, W. C., Bertelsen, R. D., & Leeworthy, V. R. (2005). Long‐term trends in the recreational lobster fishery of Florida, United States: Landings, effort, and implications for management. New Zealand Journal of Marine and Freshwater Research, 39(3), 733-747.

[6] Southeast Data, Assessment, and Review 8 (SEDAR 8). 2005. Stock Assessment Report III, Southeastern US Spiny Lobster, Section III, Assessment Workshop, Assessment of spiny lobster, Panulirus argus, in the southeast United States. Stock Assessment Report prepared by SEDAR 08 U.S. Stock Assessment Panel. Available from http://www.sefsc.noaa.gov/sedar/Sedar_Workshops.jsp?WorkshopNum=08%20B.

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