Seasonal variation in groundfish habitat associations in the Gulf of Maine–Georges Bank region

Abstract

Fish distributions are related to several habitat factors. We explored how the distribution of a 24 species assemblage is related to depth, temperature, substrate, season, and time-block using a 35 yr time series in the Gulf of Maine-Georges Bank region. We examined the relative importance of each factor, how it changes with season, and how individual species shift their relative distribution along environmental gradients on a seasonal basis. Distribution patterns were more strongly related to depth and temperature than to substrate type in both fall and spring. We observed 4 major patterns: (1) some species remained in relatively deep waters in both fall and spring; (2) some remained in relatively shallow habitats in both seasons and experienced wide temperature fluctuations as a result; (3) some moved from warmer shallow areas in the fall to warmer deep areas in the spring; (4) some traveled from the cool deep portion of the region in the fall to the cool shallow portion of the region in the spring. Of the 24 species examined, 19 declined in biomass over the study period in response to exploitation. The relationships between abundance and substrate type previously established for some species at local scales were weak at more synoptic spatial scales, although some trends in substrate associations were observed. Defining habitat at broad spatial scales remains a unique challenge. Compared to temperate systems, more refined habitat delineations for demersal marine fish have been established in tropical coral reef systems. Accordingly, much of our theory and the methodologies for applied spatial management have been derived from tropical systems. Differences between temperate and tropical systems necessitate modified approaches for temperate systems.

Compensation and recovery of feeding guilds in a northwest Atlantic shelf fish community

“…Previous studies have demonstrated non-random distributions of fishes within the region (e.g. Auster et al 2006, Methratta & Link 2006) and community boundaries have been delimited at smaller spatial scales in this LME (Overholtz & Tyler 1985, Gabriel 1992, Langton et al 1995, Auster 2002. Such community boundaries do not necessarily imply that individual fish, and hence species interactions, are bounded to those locations, but only that patterns of species composition are consistent over time in spatially limited areas.…”

Temperature‐based targeting in a multispecies fishery under climate change

“…However, the results from this analysis indicated that separability was not static either between or within years. While we expected shifts across seasons based on previous studies (Perry and Smith, ; Helser and Brodziak, ; Methratta and Link, ), we did not expect changes across years (i.e., between years with cold and warm springs). To help explain the spring results, we developed a stepwise (backward and forward) linear regression of the difference in breadth for each species between warm and cold spring.…”

“…The second mechanism is driven by the relative weight of a species’ temperature and depth preferences. Several previous studies have suggested that species with strong depth or substrate preferences (‘depth‐keepers’) are likely to be exposed to a wider range of temperatures across seasons (Murawski, ; Methratta and Link, ). Although our linear model is solely based on variables derived from species distributions in spring, the connection between the SD of (minimum) temperature and strong depth or habitat preference remains evident.…”

“…Although our linear model is solely based on variables derived from species distributions in spring, the connection between the SD of (minimum) temperature and strong depth or habitat preference remains evident. Three out of the four species with the highest SD of minimum temperature were depth‐keepers (sensu Methratta and Link): windowpane flounder (a shallow depth‐keeper), witch flounder and white hake (deep depth keepers); barndoor skate was the only temperature‐keeper (Scott, ; Gabriel, ; Murawski, ; Methratta and Link, ). Conversely, three out of four of the species with the lowest SD of minimum temperature were temperature‐keeper (spiny dogfish, American plaice, and haddock; Scott, ; Gabriel, ; Murawski, ; Methratta and Link, ).…”

“…It is also important to note that, as with numerous previous studies (e.g., Murawski, or Methratta and Link, ) we did not take into account stock structure or health, ontogenetic shifts or differences in distribution based on sex. While these variables may be significant factors affecting the distribution of various species across temperature (Murawski and Finn, ) we believe that this study provides insight into the main trends in temperature targeting in the region.…”