[Announcer] This conference will now be recorded.

[Heather Tabisola] All right, good morning everybody. Thank you for joining us today and happy Wednesday happy Spring Seminar day two, or talk two. Welcome again 2021, "Spring EcoFOCI Seminar." I am Heather Tabisola, and I co-run the series with Jens Nielsen. This seminar, is part of NOAA's EcoFOCI bi-annual seminar series that is focused on the ecosystems of the North Pacific Ocean, the Bering Sea and the U.S Arctic to improve understanding of ecosystem dynamics and applications of that understanding to the management of living marine resources. Since 1986, the seminar has provided an opportunity for research scientists and practitioners to meet, present and provoke conversation on subjects pertaining to fisheries oceanography, regional issues in Alaska's marine ecosystems, and that includes the U.S Arctic. You can visit the EcoFOCI webpage for more information at www.ecofoci.noaa.gov. And again, we thank you so much for joining us today especially as we continue in all virtual series. You can find our speaker lineup on the OneNOAA Seminar Series website and also on the NOAA PMEL Calendar of Events. We are here in March at 10:00 AM Pacific time on Wednesdays, just through the end of this month for Spring Seminar. If you've missed a seminar, we do record them and most are posted on the PMEL YouTube page. It does take a few weeks to get these up. So they are not immediate for the current seminar, but you should be able to find last season's posted. Please, double check that your microphones are muted that you are not using video. And then during the talk, please do feel free to type your questions into the chat. Jens will be monitoring the questions and we will address those at the end, with Erin. So today I'm very excited to introduce Erin Fedewa, who is a Fisheries Biologist at the NOAA Alaska Fisheries Science Center in Kodiak. Erin is a part of the Shellfish Assessment Program where she conducts research on Eastern Bering Sea commercial crab stocks. Prior to joining NOAA, She completed her master's degree at Oregon State University where she studied, "Flatfish trait variation across life history stages" "using otolith structural analysis." After completing grad school, she's worked as a research scientist for Auburn University's Marine Fish Lab. And spent a year conducting reef fish habitat research in Trinidad as part of a Fulbright research fellowship. Erin's research interests are centered around exploring how environmental variability drives changes in population processes and ecosystem dynamics. And today Erin's talk will focus on a record high Bering sea water temperatures in 2018 and 2019, that were accompanied by dramatic shifts in snow crab population structure. And will highlight the importance of ongoing and future research efforts to better understand snow crab responses to continued warming. It is my pleasure to welcome you here today, Erin. So let you take it away.

[Erin Fedewa] Awesome, thanks for that introduction, Heather. You've got me, all right, sound is good?

[Heather Tabisola] Yes we can hear you, thank you.

[Erin Fedewa] Awesome. Morning everyone. And then I go ahead and advance the slide. Thanks for having me today. I'm gonna spend a bit of time today talking about as Heather said, some recent work examining, "The effect of climate warming on snow crab," "specifically spatial distributions" "in thermal habitat use." And then from there I'd like to just highlight a few ongoing snow crab projects here at the Shellfish Assessment Program that will hopefully continue to shed light on snow crab responses to continued warming. So with that, for those of you that don't work with snow crab, this is probably a more accurate depiction of what comes to mind. Eastern Bering Sea supports one of the largest snow crab fisheries in the world. So just to give you an idea. The cap was set at 45 million pounds this year for the 2020-21 snow crab fishery. The fishery is male only and takes place in the winter with boats typically fishing right up against the pack ice. So it really makes for very dangerous conditions as well as apparently good a TV is as many of you might be familiar with. And we also can't ignore the fact that this fishery is driven by a demand for tasty snow crab legs. So now that we're all dreaming about the phase with snow crab legs, everyone's hungry here. We can put this fishery into context. Snow crab are found in Subarctic and Arctic regions. And there are populations in both the Chukchi and the Beaufort seas. This light blue shaded area shows the Southeastern Bering Sea representing the Southern extent of snow crab range. In the North Pacific where we see snow crab really concentrated on the middle shelf in the cold pool. The fishery that we just talked about is depicted by this yellow shaded region. And has historically centered on northwest of the Pribilofs and belong in Zhemchug Canyon. And this is primarily because our seasonal sea ice in the Bering Sea really has limited access to a Northern more Northern fishery grounds during this winter fishery. And we know that Eastern Bering Sea and Northern Bering Sea are really characterized as two very different ecosystems. And this is defined largely by differences in temperatures and sea ice coverage with the Northern Bering Sea functioning as an Arctic system. And that Eastern Bering Sea functioning more [mumbles] And if you watched last week's EcoFOCI seminar. Mike is a hard act to follow but he made my job a bit easier actually because he really did an excellent job explaining some of the fundamental differences between these two ecosystems. And so hopefully you can either record his talk or can watch it recorded and visit a preface to some of the work that you've done with snow crab. Well historic, snow crab distributions have really been explained by the Cold Pool and sea ice extent. We've seen that spatial patterns across the Eastern Bering Sea and Northern Bering Sea are linked to both size and sex-specific thermal requirements. At this on the left is showing catch compositions from the Northern Bering Sea and Eastern Bering Sea AFSC, bottom trawl surveys. And we can really see these latitudinal clines in snow crab population structure. So those shaded areas are showing size compositions based on immature versus mature, as well as sexes across the Northern and Eastern Bering Sea. And we really can note that on the Northern Bering Sea kinda distinguished by between that divide between our two survey grids. Cold temperatures in the Northern Bering Sea have led to historically small mature populations. So in the Northern Bering Sea we typically see few individuals that are larger than 60 millimeters carapace width. And the Northern Bering Sea really serves as a larval sink. So there's typically no commercial size males. Most of the catch is small immature, snow crab. And moving down to the Eastern Bering Sea we see kind of this variation in distribution in terms of size specific thermo requirements. So you'll note that kind of that, that northeastern corner of the Eastern Bering Sea grid is where we find most of our juvenile snow crab. And this is because they prefer these shallow cold water habitats kind of Northeast as St. Matthew Island. And we typically find mature snow crab in warmer waters off of the outer domain. And snow crab spatial distributions are characterized kinda bigger picture by these Northeast to Southwest ontogenetic migrations. And these are thought to be driven by thermal gradients. So as snow crab mature, they're really seeking those warmer waters on the outer shelf, whereas juveniles, you know really prefer those colder waters. And if you're more of a visual person like me, this is kind of what the Northern Bering Sea versus Eastern Bering Sea snow crab population structure looks like. So you'll see at that top picture is a pretty typical, you know, snapshot of catches in the Northern Bering Sea. So we see that small immature snow crab really dominate the benthic biomass in the Northern Bering Sea. Whereas that bottom picture in the Eastern Bering Sea especially if we're around areas like the Pribilofs, we tend to get a mixed catch, sometimes tanner crabs mixed in with snow crab and then to make matters worse. Those two species hybridized. So we have snow-tanner hybrids as well as kind of more of this mix of size, sex classes in the Eastern Bering Sea, depending on where we are on the shelf. And so why are these North-South distinctions important for snow crab? Well we know that these North-South boundaries that really separate Arctic and Subarctic ecosystems have begun to shift. So shown on the left, we've seen anomalous conditions in both the Eastern Bering Sea and the Northern Bering Sea. With this plot showing that 2018 marked the smallest Cold Pool and lowest ice extent on record. And then off to the right we've seen walleye pollock and Pacific cod have undergone these extensive northward migrations into the Northern Bering Sea as a potential response to a retreating cold pool. So this, you know this kind of lenses staffs asked the question, what does this mean for Arctic species like snow crab? It, you know, it's interesting to know when thinking about snow crab responses that previous studies have noted this contraction to the North of snow crab range in the Eastern Bering Sea. And this was following an increase in bottom temperatures in the late 1970s, which is shown in this figure on the left [mumbles] 2005. This evidence for climate driven range contraction suggests that continued warming could drive a similar range contraction North in snow crab and this could be driven by those specific thermal habitat requirements that we just talked about. Another potential response to warming might be a shift in population processes, for example, growth, body size, size at maturity. We've seen, snow crab that inhabit colder waters in our Northern latitudes like the Northern Bering Sea are smaller. So smaller carapace width as shown on the Y-axis of this figure on the left. As well as these crab on Northern latitudes are maturing at smaller sizes. So while changes in growth, molt frequency and maturation size could be attributed to a warmer temperatures. We might also expect that these latitudinal clines could shift also in response to migration into the Northern Bering Sea. So as this Eastern Bering Sea population that consists of you know, our larger mature individuals moving to the Northern Bering Sea and basically cause shifts in these demographic processes. So now that we've formulated some hypotheses we can begin to develop some potential mechanisms for these climate driven hypotheses. In my little cartoon under a warm scenario, as shown here. We'd expect that the suitable cold water temperatures could begin to disappear for snow crab and the Eastern Bering Sea. And as a result of the Northern Bering Sea could become relatively more important as suitable habitat. So we then I expect, as we talked about earlier to see this population range contraction northward. And it's important to recognize that with snow crab this could happen kind of via two different mechanisms. So we talked about this Eastern Bering Sea migration into the Northern Bering Sea as well as, you remember I mentioned that Northeast to southwest ontogenic migration. And if these, you know small juveniles snow crab in the Northeast are tracking thermal gradients then they may, you know as conditions form these migrations are basically shortened as the thermal gradients that they're tracking are shifting. And then kind of the other the other potential response is these shifts in demographic structure that we just talked about. So this might be via range contraction northward. And you would expect to see a potential response detected as an increase in both overall abundance and a change in the proportion of large snow crab in the Northern Bering Sea if we see evidence for this range contraction northward. As well as kind of some of these potential longer term effects such as shifts in growth, molt frequency and size at maturity. So this is a study and I just like to acknowledge my collaborators, down on the bottom right hand corner. This was just published this year. And given some of these hypotheses that we really set out to examine patterns in temperatures occupied and patterns and spatial distribution of snow crab during both cold and warm periods in the Bering Sea. So the kind of overall specific goal of this study was to evaluate the hypothesis that, increased temperatures or temperatures occupied experienced by snow crab and the potential for climate driven northward range contraction and the Eastern Bering Sea could result in this changing demographic structure of Northern Bering Sea snow crab. And so that I won't get too into the methods here, but we developed annual environmental indices to describe Eastern Bering Sea thermal conditions. [mumbles] And then on the right hand side, our snow crabs spatial indices that we've developed to examine both thermal requirements and spatial structure across multiple snow crab life history stages. So these temperatures of occupancy, spatial extent and centers of distribution were estimated across ontogenetic stages for male and female snow crab which resulted in five different size sex categories that you'll see throughout the results in the talk. From there, environmental variables were used for temperature of occupancy cross correlations and models to really look at the relative importance of environmental covariates as drivers of these snow crab spatial indices. And because we know a lot of these environmental variables are highly correlated. We used dynamic factor analysis to summarize trends in these variables. And you can see that shared trend on the left really captures that rapid warming during the 2014 to 2019, which was really, you know, outside of the envelope of observations that we have seen [indistinct] series. So again our first question, looking at trends in snow crab occupancy temperatures relative Eastern Bering bottom temperatures. That top figure, each color is a temperature of occupancy times series for a different size sex class. And that black line is the population mean. So again, we're asking if these patterns are correlated with bottom temperatures that plot on the bottom showing a mean bottom temperature. So for example, weak correlations in this case would suggest that snow crab could potentially are potentially able to buffer changes in these thermal regimes in the Eastern Bering Sea, by basically being able to maintain a constant temperature of occupancy. And just noting general trends in temperature of occupancy. We can see in 2018, you know kind of across the board for these size sex categories, we see this huge jump in temperatures of occupancy for all categories of snow crab. And this population mean was almost 3 degrees C above the mean of the times series. And then as well as these cross correlations, we saw that snow crab temperatures of occupancy were highly correlated with average bottom temperatures. It's also interesting to point out though that we see this kind of interesting three year decoupling in our immature females and small males. So if you look on that top temperature of the occupancy plot, those bottom two time series. The blue and the gray lines are immature females and small males. And basically we see in 2014 bottom temperatures in the Eastern Bering Sea increased by nearly a degree and a half C. But immature females and small males really were able to maintain temperatures of occupancy around zero degrees from 2015 to 2017. So you know, this suggests that maybe our immature, these small juvenile snow crab, were somehow able to maintain these cold water preferences despite these increasing bottom temperatures that we see at Eastern Bering Sea And a mechanism for this thermal buffering could be through as we talked about relocation to colder water habitats as the Eastern Bering Sea. So looking at distributions thorough distributions across this time period. This plot is showing abundance of a juvenile snow crab overlaid on bottom temperatures in the Eastern Bering Sea during the summer survey. We see kind of moving from left to right that juvenile snow crab really always appear in these kind of northeast nursery areas and the future Bering Sea. So typically Northeast of St. Matthew Island and these, you know nursery areas tend to be you know, in the cold pool and relatively colder, you know related to the rest of the Eastern Bering Sea. We know that these juvenile snow crab are fairly limited in terms of mobility, just because they're, you know typically 30 millimeters carapace width they're pretty small. And this really suggests that our juveniles can't seek out these preferred cold water habitats. So we kinda see, as we work along in 2018 and 2019, this preferred habitat of, you know less than two degrees C has been nearly absent in these two years. So occupancy temperatures increased dramatically as a result. And so, you know kind of the takeaway message here is that, it seems that juvenile snow crab are kind of stuck with the parts they're dealt in this case. They're, you know, based on larval infection patterns they really end up in these Northeast nursery habitats. And are just really lack the ability to relocate if the Bering Sea is warming especially in these nursery areas. So to summarize this, those couple of points that we just talked about. James Murphy actually just published a really neat paper that shows predicted posterior means of biomass for snow crab by population category, across a range of temperature values, which is shown on the bottom. And this solid line is showing specifically immature female snow crab biomass. And his results really suggest that immature snow crab specifically females are highly sensitive to temperature. And two degrees C really appears to be this temperature for our juvenile snow crab. Whereas we know based on previous studies that we really don't start to see negative effects on larger mature snow crab until temperatures exceed 6 to 7 degrees C. So potentially these warmer temperatures and the outer shell are still within the thermal threshold of our larger snow crab. Whereas a juvenile snow crab could be highly vulnerable to warming in the Eastern Bering Sea. Our second objective was to look at potential drivers of snow crab distribution. These top plot showing mean bottom temperatures there on the left with stars indicating a Northern Bering Sea to the [indistinct] for the four years that region was surveyed on our bottom [indistinct]. Yes, looking at our snow crab spatial indices that top-right plot is showing, on the Y-axis is spatial extent of snow crab [indistinct]. And again, those colored time series are five different size sex categories. You'll see that large males and females tend to have the largest spatial extent just because they have the most mobility as we've just talked about. And you'll kinda see this, you know trend and overall spatial population levels facial extent remaining well below average, since 2015. Looking at centers of distribution, there on the Y-axis of our next spatial indicator. Centers of distribution really differ greatly across our size sex categories but we kind of see these broad population level trends. So you'll kinda notice that. Centers of distribution shifted South from 2010 to 2014. And then we kinda see this reversal in a shift northward again in 2014 when we know those bottom temperatures started to increase. So we then use these environmental variables and snow crab spatial indices to look at the relative importance of a shared environmental trend on snow crab spatial extent and centers of distribution. This figure shows that the spatial extent of snow crab on the Y-axis there. Decreased significantly in relation to warming trapped by the shared environmental trend. And this response was consistent across our size sex categories. So basically what we're saying is that these increased temperatures reduced smaller, more northerly cold pool extent basically results in a smaller area occupied by snow crab. In contrary to our hypotheses, latitudinal distribution shifts were not explained by this shared environmental trends. So to summarize this, lack of support for, you know a directional shift North is obviously contrary to what we expected. Although it's interesting to know as we saw in those center of distribution trends that centers of distribution really still tend to reflect thermal regimes. So we thought that kind of five-year southward shift and then a reversal in 2014 when warming began in the Eastern Bering Sea. And then on the other side of this spatial extent of snow crab and the Eastern Bering Sea has contracted kind of in response to this warmer temperature, smaller cold pool conditions in the Eastern Bering Sea. And it's interesting that we really didn't see evidence for a density dependent range contraction, which, you know potentially suggest that these, you know climate forcing could be more important than a density dependent process you use. Although this obviously requires some further work. And so, you know kind of the take home message or the remaining question from this is, you know. Is this a reduction in spatial extent potentially due to kind of this loss of, you know this habitat that's typically utilized on the outer domain of Eastern Bering Sea. So is it potentially that in warm years these cross shelf Northeast to Southwest migrations are really contracted to the middle domain as these outer domain waters warm. And our last question in this study was to compare abundance and size structure of Northern Bering Sea snow crab across years under the hypothesis that this northward range contraction into the Northern Bering Sea might shift these latitudinal clines that we've seen from [indistinct] Bering Sea. And these two figures, these are violin plots of Northern Bering Sea male and female size distributions across the four years that the Northern Bering Sea was surveyed. So the shaded area represents probability densities of size composition data. And the box plots within those little violins summarize the median as well as 75th and 20th percentiles of population size. So the takeaways here, being that looking at males on the left first we see that median size of males in 2019 was over 25% larger than male sizes in 2010. And then kind of something similar moving to the right and looking at females we see that the median size in 2019 was 13% greater than a median size in 2010. So you know, the take home is that these size compositions that we're seeing in 2019 are a dramatic contrast to what's been previously documented in the Northern Bering Sea. And we also looked at abundances in both the Eastern and Northern Bering Sea to again evaluate this hypothesized potential shift into the Northern Bering Sea and resulting changes in Northern Bering Sea snow crab demographic structure. So this plot is showing abundance of snow crab on the Y-axis for our size sex categories that were used for this study. And how we see in the Eastern Bering Sea these really dramatic declines in small males and immature female snow crab from 2018 to 2019. So you know, you're talking females in particular immature females with 96% decrease in immature female abundance. And moving over to the Northern Bering Sea. We see these similar declines in the same size sex categories. So our small males and immature females. And these cross region declines in juvenile snow crab abundance. And then as we've just seen in the violin plot, this medium to large size males, we see this substantial increase in abundance from 2018 to 2019. Which was really confirmed in those violin plots that we saw in the last slide. So you kinda take a step back and, you know summarize some of these results. We see this distinctly different size structure in 2019. But it's, you know, it's not clear where all these large crab came from because we really didn't see this directional shift North from the Eastern Bering Sea. If we look at distributions of snow crab from the Eastern Bering Sea bottom trawl survey. I'm sorry, the Eastern and Northern Bering Sea bottom trawl survey in 2018. We can kinda see this aggregation of legal sized male snow crab. [indistinct] NBS/EBS border. And this, you know this could suggest a kind of this continuous distribution of snow crab between the two regions. And, you know, it's possible that those center of distribution spatial indices just really didn't effectively capture this shift North and in a smaller portion of the legal male, the population. And then, you know, the other side for this is that warming it could also be responsible for increased growth potential and molt frequency that might explain the presence of these large individuals in the Northern Bering Sea. We obviously can't exclude the possibility that cohorts within our Northern Bering Sea study area in 2017 could have grown to the sizes that were documented in 2019 under these warming temperatures. So this figure just depicting, you know kind of this potential or increasing size distributions being evidence of cohort growth. Suggesting that we're instead looking at this modal progression of a single cohort across years. And then going back to those dramatic declines that we saw in juvenile snow crab abundance in both the Eastern and Northern Bering Sea. Does this suggest a potential mortality event? And you'll remember that we saw those high catches of immature snow crab at Eastern Bering Sea survey stations in 2018 that were occupying temperatures greater than 3 degrees C. Followed by, you know the next year in 2019 at those same stations we see those dramatic declines. So is it possible that, you know there's some direct temperature effects on survival when they occupy those temperatures that are warmer than they really prefer. And in case you were still hungry thinking about those crab legs. This picture on the left I took on the Northern Bering Sea bottom trawl survey. This is a Pacific cod with a stomach full of their favorite prey. All of our little snow crab that we know are up in the Northern Bering Sea. And you know, this suggests that declines and immature snow crab could, you know potentially be due to increased predation. As we know, these thermal barriers are really beginning to disappear that have, you know, kind of protected juvenile snow crab from Pacific cod predation. And this plot on the right shows Pacific cod, snow crabs spatial overlap in the Northern Bering Sea. And we see this, you know, substantial increase in spatial overlap from a 43% to 88% in 2017. And then 2018 and 19, a spatial overlap was almost 100%. And then we of course, you know, really can't ignore these other confounding processes. You know, it's possible that these declines are due to selectivity as well as catchability or movement outside of the survey grid. Which, you know really, it was the kind of loss in a 2020 survey was, you know not being able to ask this question of whether this cohort materialized last year and maybe these declines in abundance could have been due to something else. So it'll be interesting to see survey results this year to the Bering Sea, you know, whether that was a mortality event. And, you know, kind of to wrap this portion of the talk up. You know, what does the future hold for snow crab? The safest answer probably is to say that I don't know. And, you know I think we've recognized that we could continue to see this broader population-level range contraction as well as, you know these predation effects on snow crab spatial distributions and demographic structure. These study results also, you know kind of emphasize the need to determine if these large males that were seen in the Northern Bering Sea are migrating southward to fishing grounds during the winter. And that might warrant the inclusion of Northern Bering Sea survey data in the stock assessment. Which currently only uses Eastern Bering Sea data. Obviously our survey results our study results are limited to kind of this small summer window during surveys. So, you know, they need to extend work to understand what these populations are doing during the winter and spring months. And as well [throat clearing] as just kinda highlighting, you know. As the Northern Bering Sea warms, this boundary between the Eastern Bering Sea and Northern Bering Sea is, you know will continue to lack biological meaning as well as you know, meaning for snow crab management. So this figure on the right is just a little screenshot of the sea ice extent and concentration. I think this was last week. Just to give you guys a snapshot of what it looks like out there right now. And this arrow is just kinda highlighting the location of the highest catches to date for the fishery that's still going on right now. So you know, these boats are really just raid up against the pack ice. And it kind of makes you question how the fleet will respond, you know. As the Eastern Bering Sea is ice free for longer alongside these potential population-level distribution shifts. So obviously, like any study, we're left with a lot of questions as we try to clarify these snow crab driver response relationships. So this slide is my shameless plug to advertise these kind of inherent difficulties in working with crab. And I'm hoping that, you know after you see this portion of the talk, you'll, maybe you'll go buy any of your crab biologists or stock assessment off your friends a beer because it's complicated. So just to, you know, provide some proof or some backup to my argument. To quantify these driver response relationships. We really need to first be able to measure these species specific responses And difficulties in determining basic crab life history parameters really leave us with a lot of data gaps and unknowns. And likewise we have, you know, I would argue that we have a pretty comprehensive understanding of pelagic energy flow in the Bering Sea and we've linked groundfish recruitment to environmental conditions, great quality and over winter mortality. But in the Eastern Bering Sea, particularly in benthic species like crab have really kind of been left out of the picture. And you know, lastly we don't really have a good understanding of what drives large changes in your class strength and I'm so proud. So I'll just take the remaining five to 10 minutes to just highlight some current research that's going on at the Shellfish Assessment Program to address some of these data gaps. And in case you were still scratching your head no crab do not have otoliths. So you know, that obviously means that we have no way to reliably age crab. We can use things like shell condition indices which are really indirect proxies and are are highly subjective. We can use a more direct method like radiometric shell age estimation. Which is based on this assumption that radium is incorporated into the exoskeleton of crustaceans which then decays to thorium with time. So we can use this technique to estimate maximum age of snow crab following their final molt to maturity. And kind of the problem here is that past radiometric studies have used our past studies used only three individuals, very old shell individuals to estimate maximum age of snow crab. Which calls into question, you know age estimates that are used in the current snow crab stock assessments. So this is a cooperative study funded through NCrab to use radiometric ageing to hopefully improve, these maximum age and natural mortality estimates in the snow crab stock assessment. And then I kind of alongside of this some more cooperative research, growth in a crab is obviously very different than fish. And is characterized by in our later benthic instar stages of crab biennial molt in the spring. So this obviously complicates things because we basically have to go out to the Bering Sea and collect these crab prior to the spring molts and then bring them back into the lab and hold them and wait for them to molt to be able to obtain these growth increment data. So you know, because of this difficulty growth models in this snow crab. Stock assessment are missing a growth for molt data across the entire range of immature sized classes. So I'm actually, I'm headed out to sea in a couple of weeks to go out there and bring these crab back to fill in some of these data gaps. And hopefully eventually get at some of these low-hanging fruit questions, you know. Temperature dependent, growth rates, and of other questions. And looking at tying those back into a changing climate. Another basic life history parameters says that, maturity is complicated because males molt maturity across a wide range of sizes. And this is accompanied by, you know morphometric changes in their chela or their large claw which you effectively have to measure to determine whether a male is mature or immature. So understanding potential shifts in size and maturity is important, because males that molt to maturity below the industry preferred size, which is shown by the black vertical line in this plot. Really, have no economic value and are thrown back as discards. So you then expect if, you know, population level size of maturity estimates decrease relative to this, you know static industry preferred size. Then effectively less males are available for harvest. And this has been a really hot topic with industry after high discards in the fishery last year, and the Bering Sea Fisheries Research Foundation just hosted you know, kind of a cross region workshop on this topic. And several great papers have just come out on it. So I'm sure there's more to come on this topic. And then you know, kinda transitioning to this understanding of benthic energy flow. Characterizing crab diets is complicated by this, you know. This lovely gastric mill, which basically functions a bit like a gizzard in a bird. So this means that, you know stomach content analysis is very difficult. It's basically impossible to ID or even quantify prey items. And we often compare a stomach content analysis with stable isotope analysis. And this is just some preliminary stable isotope analysis, we ran in 2018 showing potential variation in energy densities of snow crab. You know, collected on the bottom trawl survey. Suggesting that these energy densities really vary by sampling location. All right, so to continue some of this food habits work. We'll be running a diet study this spring in collaboration with Wes Larson at the AFSE genetics lab to pilot the use of eDNA metabarcoding to analyze crab diets. With the hopes to then expand this to obviously a survey collected crab. And then the second part to kind of understanding energy transfers, you know. This question of snow crab energetic. It's not known whether energetics could ultimately be, you know a limiting factor in juvenile snow crabs survival and recruitment success. Since past studies suggest that snow crab really rely on reaching a physiological threshold for body condition and require baseline energetic stores to survive through the molting process. So indirect proxies like our length weight, residuals are really insensitive for crab. Whereas more direct methods like lipid and fatty acid analysis really allow us to directly quantify things like body condition, energy, allocation and snow crab relationship. And so Louise Copeman lead a recent study showing that juvenile snow and tanner crab collected in a warm year in the Eastern Bering Sea had lower total fatty acids and diatom fatty acid biomarkers than crab collected from a full year [mumbles] in the Eastern Bering Sea. With this figure on the left here showing annual and regional differences in that diatom indicator. So these results are exciting. Because they really provide some of the first evidence linking warming events to reduce energetic condition, as well as kind of highlighting the importance of diatom production for snow crab. And we'll continue this work. Louise and I are working on an NPRB-funded project to quantify variation in energy or energetic condition of in these energy allocation patterns. And then we link these energetic patterns to bond futures and snow crab [mumbles]. And then, yeah okay. Lastly this, you know ultimate black box of early life history. Understanding recruitment variation and early life history dynamics for snow crab. To date very few studies have been conducted on larval snow crab. But Buck Stockhausen has been working on a spatially-explicit IBM for snow crab. Which uses the ROMS model physical environment with these end locations for simulated successful and unsuccessful snow crab. Based on temperature dependent interim alterations that he's included in these simulations. So I don't wanna steal his thunder here but this is an example I'll put of some of his results with those red dots showing unsuccessful individuals that didn't reach nursery habitats by the end of the simulation based on different start zones. And modeling applications like these really obviously benefit from a field collected data to validate these spatial temporal distributions of snow crab larval stages. To date you know, NOAA larval surveys don't typically ID decapods to species [mumbles] working this spring to collect some ichthyoplankton samples from the EBS mooring survey to start up some of this early. And then with that, you know kind of maybe a strange closing slide. But to put all these pieces together is this, you know this obviously bigger picture effort towards ecosystem-based fisheries management. Ecosystem and Socioeconomic Profiles, or ESPs, have been developed to kind of serve as a proving ground for testing these ecosystem and socio-economic linkages within the stock assessment. And so I've been leading kind of the E-portion of the ESPs and we're gearing up to start a snow crab ESP this year. And you know, I guess I'll close with saying in trying to develop effective ecosystem indicators it's really a great chance to talk to you all and, you know hear what you've been doing and how your research might contribute to, you know developing some of these ecosystem indicators. So I'll close with just saying that, you know I'd love to hear from you if you have data to contribute. I'd love to hear from you regardless. And it's been super fun to talk about crab. So with that, I'd be happy to take any questions.

[Heather Tabisola] Awesome. thank you, Erin. [Applauds] I always do claps because well, nobody else can. So here we are. [laughing] It's weird as it sounds. We actually have about five minutes. So I just want in our hour blocks. So I wanna give folks the opportunity. We will be here again next week. Dr. Calvin Mordy and Dr. Bonnie Chang will be talking about nutrients in the Chukchi Sea. And again, this meeting has been recorded. So if you need to catch up on that or the questions that we can take following on. Please feel free to message Jenss and I and we can address that. Or please also reach out directly to Erin, and you can send your followup questions to her as well. With that I think, Erin if you have the time, I know...sorry. I was just double checking. I know Romundo was doing her presentation following. So I wanna be mindful of that as well. And that does start at 11:00. So I'm gonna give folks, we'll cover the questions and I'll say we have like another five minutes to go over questions. And then after that, we'll have to close the seminar. So Erin really amazing talk and I'm sure everybody else on here knows this. I did not know that cod ate crab. And I am literally in my mind trying to figure out how their system digests it right now. So that's what I'm 100% focused on, but [laughing] at the end we'll meet, he already knew that as well. So I clearly am just the last person in the world to know this. And okay, so I'm just gonna go back and read some questions that were already on here. And if folks have new ones again please feel free to put them in the chat or just reach out to Erin directly. So one of the questions that had come in before is from William or Bill Stockhausen. And he had asked early on snow crab instar sizes are reportedly extremely conservative in Eastern Canada. Is this true in the Bering Sea across latitudes? So shifts in mean size reflect fewer molts prior to maturity?

[Erin Fedewa] Yeah, great question Buck. You know, kind of the the idea behind these latitudinal clines, part of it, yes, is, you know, this variation and inter molt duration. So based the colder temperatures, it takes longer for crab obviously. So this you know, duration is temperature dependent. But we also see, and I'm sure Buck is familiar with this. In cooler temperatures, we see skip molting more frequently. So because crab are kind of hunkered down in these really cold conditions. The, you know they tend to skip molts and because of that they really just reach these smaller sizes at maturity. And I'm sure I'm sure Buck can actually even add elaborate more on that too.

[Heather Tabisola] And Libby had also asked, "What might be the mechanism for different temperature preferences of immature and adult crab?"

[Erin Fedewa] Yeah, that's a good question. You know, inherent mechanism, that's a tough one. You know, the thing that comes to mind is that I think largely a temperature preference, you know it could just be that these immature snow crab really need these colder waters to be able to avoid predation from Pacific cod that typically don't inhabit, you know these less than 2 degrees C water. So it could just be that we tend to find them in these colder waters because they're able to evade predators. Typically Pacific cod unless they're a soft shell crab, cod really aren't feeding on, you know, larger mature snow crab just because they're too big in terms of gape width. So you know, this preference could just be because we've historically seen them there as kind of a you know, adaptation, if you will to really avoid these predators like cod. But yeah, that's a great question. I'm gonna have to follow up with that.

[Heather Tabisola] All right, there's the couple of questions on here from Jesse and I think a follow-up from Buck. But I'm gonna actually skip to Melanie's question. [laughs] Which is, "How would you characterize the cross shelf use by snow crab inner versus middle versus outer domains, is there more North South movement during their life cycle or is it more movement East West also important?"

[Erin Fedewa] Yeah great question as well. For snow crab it really seems to be that kind of Northeast to Southwest as I've said. But I would say directionally more North to South and we've kinda seen some recent papers come out that suggests with projected warming we'll continue to see these shifts North. Whereas a species like tanner crab we might see more of these East-West shifts in distribution. So yeah, cross shelf, if that answered the question I would definitely say more North to South movement. Just because it seems that that Northern brings to you is really kind of a larval sink. And then we see all those mature crabs down in. you know, Southern portions of the Eastern Bering Sea. So it really, you know lends to suggesting that North-South movement is more important.

[Heather Tabisola] Awesome. All right and then Jesse's question and we'll end with this one. Is rearing these crabs in the laboratory conditions possible? And then he was guessing that maybe there's issues with cannibalism, certain sizes similar to other species and lobsters and, yeah.

[Erin Fedewa] Yeah many issues with cannibalism. And the the grill study is a great example of that. So crab love to eat each other when they're little when they're soft shell, they're like little monsters. So in a study like the grill study when we know crab are molting, you might've seen that picture of the crab and the Tupperware. We actually have to isolate every single crab so that they're not eating each other. And if you were going to chance to, you know if you're ever up in Kodiak, we'd love to show you, well, maybe post COVID. [laughs] We'd love to show you the sea water facility 'cause it's pretty impressive what the group here has been able to do in the lab in terms of rearing. And we've had, you know overall great luck with rearing them. Snow crab larvae really is the difficulty in terms of rearing larvae. But I know Newport has had good luck with that. So Red King crab larvae you can definitely rear. But yeah, it's you have to be mindful of it's like cannibalism for sure.

[Heather Tabisola] Are they as cannibalistic in the ocean as they are in like a tank?

[Erin Fedewa] Yeah if population densities are high enough it's kinda assumed that, you know. It's interesting that some studies have tried to factor in cannibalism, you know. A lot of it in the field, we just don't know but I would assume so they really like to eat each other.

[Heather Tabisola] I always think of the images of Blue Planet when like I never knew crabs did this. But like those mass amounts of crabs and they're just crawling over each other and I never dawned on me but it was pretty cool to see, yeah. All right, Erin thank you so much. I'm gonna end recording here. Thank you for those who are still with us. Again, if you have questions, please reach out to Erin directly or with like her slides. Again, recordings of the talks from this season will be up in a few weeks, so they are not immediately available. And you can find the rest of the schedule on the OneNOAA Science Seminar website or also at the NOAA Pacific Marine Environmental Lab Calendar of Events. Thank you guys for joining us today.