3 Relevance to valuable fisheries
The National Marine Fisheries Service prioritizes optimizing stock yields, preventing overfishing, and enhancing climate and economic resilience within the U.S. seafood and fishing sectors (NOAA Fisheries 2022). Achieving these goals will require ongoing scientific advancements to support adaptive fisheries management in the face of shifting ecosystem dynamics (NOAA Fisheries 2024). My research will greatly expand our ability to accurately and non-invasively estimate crustacean size at maturity. The results of this project will be directly applicable to the establishment of minimum landing sizes and the development of stock assessment models for dozens of U.S. fisheries. Here, I provide evidence for the utility of modeling morphometric maturity for the management of specific crustacean species that support economically valuable U.S. fisheries.
3.1 Jonah crab
Scientific name: Cancer borealis
Selected publications related to morphometric maturity: (A. E. Lawrence 2020; A. Lawrence et al. 2021; N. A. Olsen and Stevens 2020; Moriyasu et al. 2002)
| Relevant research priorities | Source |
| “Better knowledge of the Jonah crab reproductive biology, particularly maturation rates (e.g., age-at-maturity) … would be useful to gain greater insight into crab population dynamics and vulnerability to overfishing.” Under 2.3.2: Size-at-Maturity: “We recognize additional modeling approaches need to be developed to better stabilize these models and improve performance.” |
Jonah Crab Benchmark Stock Assessment and Peer Review Report, 2023 |
| Reproductive studies pertaining to male-female spawning size ratios, the possibility of successful spawning by physiologically mature but morphometrically immature male crabs, and potential for sperm limitations should be conducted | Research Priorities and Recommendations to Support Interjurisdictional Fisheries Management: JONAH CRAB |
| Research growth mechanisms for both sexes (e.g., potential for terminal molt, lack of growth associated with molting, high natural mortality for adults) to explain lack of exploitation signal (i.e., lack of size structure change) in available data sets. | Research Priorities and Recommendations to Support Interjurisdictional Fisheries Management: JONAH CRAB |
3.2 American lobster
Scientific name: Homarus americanus
Selected publications related to morphometric maturity: (Templeman 1935; Waller et al. 2021; Émond, Sainte-Marie, and Gendron 2010; Little and Watson 2005; Comeau and Savoie 2002; Landers, Keser, and Saila 2001; Conan, Comeau, and Moriyasu 2001)
| Relevant research priorities | Source |
| “The Review Panel found all aspects of growth were very high research priorities, e.g., …, continued monitoring and study of changes in size at maturity due to its influence on growth” Under 8.2 - Research Recommendations a. Maturity (Medium Priority) … Future maturity work should focus on additional statistical areas with large landings contributions. Exploration of non‐invasive techniques to assess maturity are also desirable, allowing for more frequent and efficient updates to maturity estimates. Methods to allow for time‐varying maturity in the assessment model should also be explored, to better capture the influence of a changing environment on lobster population dynamics. Finally, it is extremely important for the newly updated maturity data to be applied towards updating the growth matrix underlying the assessment model |
2020 American Lobster Benchmark Stock Assessment and Peer Review Report Research Priorities and Recommendations to Support Interjurisdictional Fisheries Management: AMERICAN LOBSTER |
| “Up to date female size at maturity studies and accompanying biological measurements are necessary for future assessment and management efforts.” “This work highlights the need to update historical maturity datasets as these measures of lobster development and growth are integral to evaluations of the size-based regulatory tools used in the management of the American lobster fishery.” |
Waller et al. (2021) |
| “As the region continues to experience significant changes in the fishery and rates of warming, accurately characterizing size at maturity for female lobsters is key to assessing both reproductive potential and growth rates.” “The spatial differences in size at maturity observed here reinforce the need to document potential changes in life history traits over the American lobster’s geographical range” |
Ellertson et al. (2022) |
3.3 Blue crab
Scientific name: Callinectes sapidus
Selected publications related to morphometric maturity: (Thienes 2023; Olmi and Bishop 1983; Waugh et al. 2009; Z. Olsen, Wagner, and Sutton 2016; Marchessaux, Gjoni, and Sarà 2023; Newcombe, Sandoz, and Rogers-Talbert 1949)
| Relevant research priorities | Source |
| “Evidence of a decreasing female size-at-maturity in the Chesapeake Bay could suggest that the productivity of the population is decreasing. CBSAC suggests prioritizing research studies that aim to address data gaps related to blue crab fecundity and population productivity to better understand trends in abundance.” | Chesapeake Bay Stock Assessment Committee (CBSAC) Blue Crab Workshop Report, 2022 |
| “Knowledge of the species’ life history traits in Florida remains inadequate for a complete and accurate stock assessment. Specifically, much remains unknown about blue crab reproductive biology, seasonality of spawning, and recruitment patterns.” | Hart, Crowley, and Walters (2021) |
| “Research on the variability of reproductive parameters (e.g., maturity, fecundity and batch production) is a high priority.” | Stock Assessment of Blue Crab in Chesapeake Bay, 2011 (most recent complete stock assessment) |
3.4 Snow crab
Scientific name: Chionoecetes opilio
Selected publications related to morphometric maturity: (Bakanev and Pavlov 2023; Mullowney and Baker 2021; Catlin 2020; Divine et al. 2019; Dawe et al. 2012; Burmeister and Sainte-Marie 2010; Orensanz, Ernst, and Armstrong 2007; Hébert et al. 2002; Mayrand, Guderley, and Dutil 1998; Claxton, Govind, and Elner 1994; Warren 1994; Comeau and Conan 1992) (extremely large body of research)
3.5 Atlantic deep-sea red crab
Scientific name: Chaceon quinquedens
Selected publications related to morphometric maturity: (Stevens and Guida 2016; Martínez-Rivera, Long, and Stevens 2020; Haefner 1977)
| Relevant research priorities | Source |
| “Studies to evaluate reproduction and sexual maturity are needed to estimate biological reference points and key parameters for fisheries management and stock assessment models.” | Martínez-Rivera, Long, and Stevens (2020) |
| “Traditional reference points for the deep sea red crab stock are difficult to estimate due to lack of basic information.” “The [Peer Review] Panel prioritized the collection of growth and natural mortality information… and simulation modeling to develop reference points appropriate for this species’ life history as the most important areas of research to move the assessment to a more analytical approach.” |
NEFSC Management Track Assessments, Spring 2023 |
| “Deep-sea red crab is a data-poor species with little known of its growth or longevity… There is scant information on biological parameters of red deepsea crab, such as size at maturity, fecundity, or timing of reproduction.” | Stevens and Guida (2016) |
3.6 Dungeness crab
Scientific name: Metacarcinus magister
Selected publications related to morphometric maturity: (Wainwright and Armstrong 1993; Worton et al. 2009; Collier 1983; Butler 1961)
| Relevant research priorities | Source |
| “Our study offers a first step toward evaluating the functional maturity and legal size limits of Dungeness crab, but until functional maturity can be defined in a competitive setting [and] a full functional maturity schedule is determined … changing the size limit is not recommended.” | Worton et al. (2009) |
3.7 King crab
Scientific name: Paralithodes spp. & Lithodes spp.
Selected publications related to morphometric maturity: (Wallace, Pertuit, and Hvatum 1949; Somerton and MacIntosh 1983; Filina 2011; Stevens and Jewett 2014; Pengilly, Blau, and Blackburn 2002; Olson, Siddon, and Eckert 2018; Paul and Paul 2000; Somerton and Otto 1986; Sloan 1985; Jewett, Sloan, and Somerton 1985; Somerton 1981a)
| Relevant research priorities | Source |
| “Size at maturity has not been determined specifcally for Pribilof Islands red king crab males.” | 2022 (triennial) assessment for Pribilof Islands red king crab |
| “Specific research on St. Matthew Island blue king crab life history parameters is not available and therefore data are borrowed from other stocks/species.” | 2024 assessment for Saint Matthew Island blue king crab |
| “Size at maturity of NSRKC is highly uncertain.” Male crab size at maturity is listed as a “critical model assumption” |
2024 assessment for Norton Sound red king crab |
| “Along with a lack of annual survey data, limited stock-specific life history stock information prevents development of a comprehensive length-based assessment model.” Under Research priorities: Male size at maturity |
2024 assessment for Aleutian Islands golden king crab |
| “Size at maturity has not been estimated for WAI male red king crab.” | 2023 (triennial) West Aleutian Islands red king crab |
3.8 Stone crab
Scientific name: Menippe spp.
Selected publications related to morphometric maturity: (Zambrano and Ramos 2020; Crowley et al. 2018; Reeves et al. 2017; Gerhart and Bert 2008; Bertini et al. 2007; Restrepo 1989; Bert et al. 1986)
| Relevant research priorities | Source |
“Transitioning to more sophisticated stock assessments, which would allow more effective fisheries management, will require detailed information on population biology, specifically, size at reproductive maturity.” “The development of accurate estimates of size at sexual maturity in stone crabs must use all available indicators of maturity and must include studies conducted throughout the range of the fished stock.” |
Crowley et al. (2018) |
“Assessment of the heavily exploited stone crab in Florida requires accurate descriptions of the reproductive biology and population dynamics of the stock.” Crowley et al. (2019) developed an an age-structured model that utilized the new size at maturity information published in Crowley et al. (2018). The model estimates of spawning potential ratio (SPR) were sensitive to the assumed size at sexual maturity, demonstrated the sensitivity of estimated biological reference points to the input life-history parameters and highlighting the need for continued research into stone crab maturity. |
Crowley et al. (2019) |
3.9 Tanner crab
Scientific name: Chionoecetes bairdi
Selected publications related to morphometric maturity: (Stevens et al. 1993; Paul and Paul 1995; Otto and Pengilly 2002; Stone, Masuda, and Clark 2003; Fong and Dunham 2007; Murphy 2021; Richar and Foy 2022; Somerton 1981b)
| Relevant research priorities | Source |
| “In many years our size at 50% maturity estimates were well below the regulation legal retention sizes… Further research into this issue, and careful monitoring in future years should be a priority.” | Richar and Foy (2022) |
3.10 Caribbean spiny lobster
Scientific name: Panulirus argus
Selected publications related to morphometric maturity: (Anderson et al. 2013; Atherley et al. 2021; Tewfik, Babcock, and Phillips 2020)
| Relevant research priorities | Source |
| Under 7.1 Research Recommendations: More basic biological studies to improve understanding of key life history processes such as growth, length/age at maturity, fecundity, and their spatial variability. |
SEDAR 57 Stock Assessment Report, 2019 (most recent completed stock assessment) |
| “Our study focused on size at sexual maturity in females, but based on our data, similar studies should be conducted on males.” “Our findings underscore the importance of using locally derived reproductive data for regulatory decision making… Territories lacking recent data are advised to assess their P. argus populations using the techniques presented here.” | Atherley et al. (2021) |
3.11 Pandalus shrimp
The genus Pandalus includes many species of shrimp that are economically valuable for the United States fishing industry. Commercial fishing occurs for ocean shrimp (P. jordani) off the coast of Washington, Oregon, and California, while spot shrimp (P. platyceros) are targeted throughout their geographic range from Southern California to the Aleutian Islands in Alaska (Levy et al. 2020). Other shrimp of commercial and subsistence value in Alaska include the Alaskan pink shrimp (P. eous), the humpy shrimp (P. goniurus), the humpback shrimp, (P. hypsinotus), and the sidestripe shrimp (P. dispar).
On the Atlantic coast, the northern shrimp (P. borealis) supported a large fishery in the Gulf of Maine for decades but is now extremely depleted and commercial fishing for northern shrimp is prohibited. Despite the fishing moratorium that has been in place since 2014, the most recent stock assessment update (December 2024) reported a continued decline in stock status, with all indices at all-time lows (Atlantic States Marine Fisheries Commission 2024). Although a small number of fishing industry members will be allowed to catch P. borealis in 2025 through a winter research sampling program run by the Maine Department of Marine Resources and the Atlantic States Marine Fisheries Commmission, Draft Amendment 4 to the Fishery Management Plan suggests that it may be a long time before harvesting is permitted outside of such sampling pilots. The draft states that “given the continued poor condition of the stock, the requirement of annual specifications in the Northern Shrimp FMP may no longer be appropriate” and proposes lengthening specification timelines to allow for multi-year moratoriums (Atlantic States Marine Fisheries Commission 2025).
Pandalus species are difficult to model using traditional stock assessment methods because they are protandric sequential hermaphrodites; i.e., they reproduce as males before changing sex to become female (Bergström 2000). Along with the size at which the sex transition occurs, their growth rate, recruitment dynamics, and natural mortality can be highly sensitive to changes in environmental conditions (Chang, Richards, and Chen 2021; Hansen and Aschan 2000; Perry, Boutillier, and Foreman 2000; Hannah 2011). Rather than including a size at 50% maturity (SM50) parameter, current P. borealis stock assessment models include a parameter \(L_{50_{sex}} (y)\), the length at which 50% of shrimp change sex to females in year y (Drouineau et al. 2012; Cao, Chen, and Richards 2017a). A statistical catch-at-length model model that includes environmental variables (Cao, Chen, and Richards 2017a, 2017b) utilizing such a sex change function is now preferentially used for P. borealis management over catch-survey analysis (CSA) and Age Structured Assessment Program (ASAP) models used in previous analyses (Cadrin et al. 1999; Atlantic States Marine Fisheries Commission 2021, 2018). The notable plasticity of \(L_{50_{sex}}\) in Pandalus means that it is useful as an indicator of population status; for example, comparing annual \(L_{50_{sex}}\) values to established baselines is an important component of the management of the P. platyceros and P. hypsinotus fisheries in Southeast Alaska (Smith 2020). Because fecundity increases with size for Pandalus species, decreases in \(L_{50_{sex}}\) result in decreased population fecundity, which can lead to lower recruitment and further reductions in population size (Smith 2020).
Multiparous and primiparous females can be easily differentiated by sternal spines that are only present in females who have not previously spawned (McCrary 1971). This criterion was used by Skúladóttir and Pétursson to calculate median length at maturity for P. borealis (an example of determining SM50 based on functional maturity) in the Denmark Strait, finding geographic variation in SM50 between three different areas in the waters around Iceland (Skúladóttir 1998; Skúladóttir and Pétursson 1999). In conjunction with the general hermaphroditic structure of their life history, this means that morphometric maturity is not generally a highly relevant notion for Pandalus shrimps. However, morphometric analyses have been used to discriminate between populations of P. borealis from different Icelandic fjords (Jónsdóttir, Guðlaugsdóttir, and Karlsson 2016).
In summary, although size at maturity and morphometric analysis are separately important for Pandalus, size at morphometric maturity does not appear to be relevant for the U.S. fisheries for species within the genus.