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In order to define the relative vulnerability of northern shrimp ( Pandalus borealis ) populations to the ongoing global warming, we compared the thermal performance curves for survival and growth in the first three pelagic larval stages from three populations of the Northwest Atlantic. Egg carrying females were obtained from different regions characterized by distinct sea surface temperature (SST) conditions for larval development in spring. Two independent experiments were conducted in two different years. In spring 2012, larvae from females captured in the Lower St Lawrence Estuary (LE) and in the Northeast Gulf of St Lawrence (GSL) were compared. In spring 2014, larvae from females captured in the LE and on the Labrador–Newfoundland Shelf (Northwest Atlantic, NWA) were used. The LE larvae were used both years and served as the reference population for comparisons. In 2012 and 2014, groups of 25 newly hatched northern shrimp larvae from each source population were incubated at six temperatures (0, 3, 6, 9, 12, and 15 °C) to monitor and compare survival and growth at moult. Northern shrimp larvae from the LE (warmer May–June SST) had a higher optimal temperature range for survival compared to larvae from the GSL and the NWA (colder May–June SST) populations. However, in 2012 growth performance at moult was reduced at higher temperatures for the LE population compared to the GSL population. The differences in thermal performance curves observed may suggest the presence of a certain level of local adaptation in response to the different regional SST regimes in spring–early summer. Northern shrimp larvae in the Northeast Gulf of St Lawrence and Northwest Atlantic shelf could benefit from warmer early-spring temperatures; however, larvae from the Lower Estuary may be closer to their upper tolerance limits and thus more likely at risk of negative impact of future warming of surface water masses. [ABSTRACT FROM AUTHOR]

Ouellet, P., Fuentes-Yaco, C., Savard, L., Platt, T., Sathyendranath, S., Koeller, P., Orr, D., and Siegstad, H. 2011. Ocean surface characteristics influence recruitment variability of populations of northern shrimp (Pandalus borealis) in the Northwest Atlantic. – ICES Journal of Marine Science, 68: 737–744.Remotely sensed data were used to derive simple ecosystem indicators for four regions of the Northwest Atlantic to test the hypothesis that sea surface temperatures (SSTs) and spring phytoplankton bloom characteristics (initiation, timing, intensity, and duration) have a significant influence on larval survival and recruitment of northern shrimp (Pandalus borealis). For all years (1998–2007) and regions, hatching was after the initiation of the bloom and before or after the bloom reached its maximum intensity. The results suggest that the best survival of larvae is associated with high warming rates of SST following hatching, but in very cold environments, warm temperatures at hatching seem to be important for larval survival. The analyses also indicate that larval survival is supported by an early, long phytoplankton bloom which attains high concentrations of chlorophyll a. The results demonstrate the potential of remotely sensed data for deriving simple population-specific ecosystem indicators for potential use in building operational recruitment models for predicting changes in northern shrimp abundance. [ABSTRACT FROM PUBLISHER]

By combining field data and laboratory observations of larvae in a simulated thermal gradient, we described the ontogenetic changes in vertical distribution and behaviour of early stages of shrimp Pandalus borealis in thermally stratified water columns. Both in the laboratory and at stations in the north-western Gulf of St Lawrence, the first two larval stages appear to actively select and maintain a position in the upper layer of warmer temperatures, within the thermocline and above the cold (<1°C) intermediate layer. Stage III larvae were distributed deeper in the water column and in colder waters than the previous two stages. Stage IV and V larvae showed the highest degree of swimming activity in the laboratory and a much wider range (from surface to ∼200 m) in vertical distribution in the field. The shift to deeper waters and settlement to the bottom habitat appears to happen after the fifth moult, at stage VI. We propose that the pattern of vertical distribution in the field reflects the adjustment of the different developmental stages to the distribution of preferred prey. The description of the ontogenetic change in the vertical distributions and movements of early stages of P. borealis should be valuable information for future attempts to model larval transport and dispersion, and for detecting settlement/recruitment areas using 3D ocean circulation models. The identification of the thermal habitat of the different larval stages and the timing for settlement at the bottom also provides important information for the development of temperature-dependent growth models up to the first juvenile stages. [ABSTRACT FROM AUTHOR]

Northern shrimp Pandalus borealis (Krøyer) larvae hatch in the northern Gulf of St. Lawrence from early May to the end of June, and larval development occurs over a range of relatively cold water temperatures. Because of the long duration of the pelagic phase and the difficulty of sampling all successive larval stages at sea, we used laboratory experiments to assess the effects of water temperature on larval development and growth. In spring 2000, P. borealis larvae were reared from hatching to the first juvenile stages (i.e., stage VI and VII) at three temperatures (3, 5, and 8°C) representing conditions similar to those in spring in the northern Gulf of St. Lawrence. Larval development and growth were dependent on temperature, with longer duration and smaller size (cephalothorax length, CL, and dry mass, DM) at 3°C relative to the 5 and 8°C treatments. There were no significant differences in the morphological characters of the different stages among treatments, indicating that regular moults occurred at each temperature. The results suggest a negative impact of cold temperatures (lower intra-moult growth rates and smaller size) and, possibly, higher cumulative mortality due to longer development time that could affect the success of cohorts at sea. However, CL and DM for stage III and later larvae were smaller than those of larvae identified at the same developmental stage in field locations. It is possible that the diet offered to larvae in this experiment ( Artemia nauplii, either newly hatched nauplii or live adults, depending on the developmental stage) was not optimal for growth, even though it is known to support successful P. borealis larval development. In the field, there is the possibility that phytoplankton contributes to the larval diet during the first stages and stimulates development of the digestive glands. Furthermore, the nutritional quality of the natural plankton diet (e.g., high protein content, fatty acid composition) might be superior and favourable to higher growth rates even at lower temperatures. [ABSTRACT FROM AUTHOR]

Larvae of the northern shrimp Pandalus borealis (Krøyer) are pelagic. In the Estuary and Gulf of St. Lawrence, Canada, the early stages are found in the upper 25-m of the water column in spring and early summer and are expected to experience a range of water temperatures from as low as 0°C to as high at 6°C. Little is known of the impact of water temperature on metabolic requirements of northern shrimp larvae. In this study, routine respiration ( VO2), maximum respiration (electron transport system activity, ETSA) and metabolic scope for growth (MS, ETSA– VO2) of northern shrimp larvae were measured as a function of temperature (3, 5 and 8°C), developmental stage (I–V at 3°C, I–VII at 5°C and 8°C) and growth rate in dry mass. After logarithmic transformation, all three metabolic variables were linearly related to dry mass. The increase in VO2 with body mass was faster at 5°C than at 3 or 8°C, whereas with ETSA this increase was slower. As a result, MS increased more slowly with dry mass at 5°C than at 3 and 8°C. However, MS did not limit growth in this study, since it explained only 39% of the variability in growth. All three metabolic variables as well as growth varied together as a function of temperature and ontogeny. Q10 of all three metabolic variables ranged from 1.6 and 2.2 for stages I–V larvae, except for VO2 at stage I (3.9) and stage III (2.9). [ABSTRACT FROM AUTHOR]