Spatiotemporal variability in the phenology of the initial intra‐annual molt of American lobster (Homarus americanus Milne Edwards, 1837) and its relationship with bottom temperatures in a changing Gulf of Maine

Abstract

This study uses the Maine Department of Marine Resources Lobster Sea Sampling data (2000–2016) and logistic models to develop the first time series for the timing and suddenness of onset of the initial intra‐annual molt of American lobster in the Gulf of Maine (GoM), an annual fishery recruitment event crucial to fishermen. Data from three GoM regions (eastern, central, and western coastal Maine) were further divided by sex and estimated maturity of sampled lobsters for analysis. We found differences in the patterns of initial molt timing and suddenness between the regions, sexes, and stages of maturity. Using the Northeast Coastal Ocean Forecasting System hindcast temperatures, seasonal accumulated degrees above 5°C were used to describe the thermal history for each region at ocean depths of about 5 and 110 m. These temperature metrics were used in generalized linear models to investigate the potential effects of seasonal temperatures on the initial molt season. Results showed that initial intra‐annual molting of lobsters was variable from 2000 to 2016, with periods of both earlier and more sudden molts and later and more protracted molts. Warmer temperatures, specifically inshore temperatures, were generally associated with an earlier molt, but without complete uniformity in the direction and magnitude across seasons, regions, and lobster demographics. We also discuss why developing molt time series and quantifying the connection to the bottom temperatures are necessary and emphasized why existing monitoring programs and the applied quantification techniques herein make this relationship difficult to quantify.

Examining Scale Dependent Environmental Effects on American Lobster (Homarus americanus) Spatial Distribution in a Changing Gulf of Maine

“…We developed a modeling approach to explore and demonstrate how estimates of season-, sex-, and size-specific American lobster spatial distribution and abundance would vary based These results correspond with the notion that local patterns may get masked by global statistics, if stationary assumptions are made (Brunsdon et al, 1996;Windle et al, 2012). Stationary assumptions are likely to be violated in the GOM, where northeast to southwest gradients of bottom water temperature, salinity, and productivity have been observed (Lynch et al, 1997;Pettigrew et al, 1998;Chang et al, 2016), as well as spatial differences in American lobster stock-recruitment relationships (Chang et al, 2016), and spatially varying patterns in initial molt timing and suddenness (Staples et al, 2019).…”

“…area of possible mixing between currents could throw off GAM relationship curves if the this area were to be included into a particular side. One previous study used a similar trisected approach to view relationships between initial intra-annual molts of American lobster and bottom temperatures in the GOM (Staples et al, 2019). Consequently, the second set of localized models (West-GAM, Central-GAM, and East2-GAM) are built in in such a way that the West-GAM is the same in spatial area and extent as previously described, but the Central-GAM is comprised of data between −69.27457 and −68.58246 degrees longitude, and the East2-GAM is comprised of data east of −68.58246 degrees longitude.…”

“…(Brunsdon et al, 1996;Fotheringham et al, 2002). Past literature has demonstrated evidence of spatial nonstationarity in the GOM region (Li et al, 2018;Staples et al, 2019). Accounting for nonstationarity in SDMs allows for the incorporation of spatial and/or temporal dependencies that cannot be explained by environmental variables alone (Bakka et al, 2016).…”

Spatial and temporal patterns in the sex ratio of American lobsters (Homarus americanus) in southwestern Nova Scotia, Canada

“…These two LFAs experience different oceanographical conditions as LFA 34 is adjacent to the Gulf of Maine while LFA 33 is situated on the Atlantic Ocean 38 , 39 . Different ocean currents, their velocity and direction, ocean productivity or the benthic habitat can influence the salinity, abundance of predators as well as larval recruitment and settlement which are important factors for lobster distribution 17 , 39 – 42 . However, we did not have access to these data to account for any effects on sex ratio in our study.…”

Shifting Transcriptomes In Changing Waters

“…In particular, the Northwest Atlantic Ocean is one of the fastest warming regions (Pershing et al 2015;Saba et al 2016;Le Bris et al 2018), with the GoM warming at rates four to seven times faster than the global average in recent years (Thomas et al 2017;Carlowicz 2018). While research on ocean change in the GoM accumulates (Mills et al 2013;Pershing et al 2015;Pershing et al 2018;Le Bris et al 2018;Staples et al 2019) and suggests a potential warming of 0.5-3.5 °C in the region by the year 2100 (Fernandez et al 2020), the implications of the warming waters on its marine inhabitants remains to be fully elucidated.…”