Phenological shifts in hatch timing of northern shrimp Pandalus borealis

Richards, R. A.

doi:10.3354/meps09717

Cited by 26 publications

(33 citation statements)

References 22 publications

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“…Previous studies in similar environmental conditions showed that hatching of northern shrimp eggs occurs over a short period (1–2 days in Bergström, ; 20 days in Pedersen et al., ; 44 days [range from 16 to 78 days] in Richards, ) from April to May; specific timing may vary from year‐to‐year and likely correlates with water temperature (Koeller et al., ; Ouellet & Chabot, ; Ouellet et al., ; Pedersen et al., ; Shumway et al., ). These sources of variation may have important consequences for connectivity among management units given major changes in environmental and oceanographic conditions during the transition from spring to summer (Han et al., ).…”

Section: Methodsmentioning

confidence: 94%

Assessing connectivity patterns among management units of the Newfoundland and Labrador shrimp population

Corre

Pepin

et al. 2018

Fisheries Oceanography

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The Eastern Canadian northern shrimp population, representing one of the most important fisheries in the region, decreased dramatically since the mid‐2000s to a historical low in 2017, but changes were not spatially uniform. Applying a biophysical model within Newfoundland and Labrador (NL) management areas, we investigated connectivity processes during the long pelagic larval phase (2–3 months) of Pandalus borealis and key drivers of larval dispersal in different environmental conditions. We selected 3 years representative of contrasting North Atlantic Oscillation (NAO) phases to assess potential larval dispersal patterns of the northern shrimp population in NL, and hierarchically assessed the impact of the timing of release (yearly and daily), release location, and vertical migration behaviour on shrimp larval dispersal. Overall, we found that populations located on the northern Newfoundland and Labrador shelf supplied potential settlers to southern populations because of the dominant Labrador Current. Ocean circulation and current velocities during the NAO positive year differed from other years, generating contrasting settlement spatial patterns. Larval release location and vertical migration behaviour were the two most important influences on the strength of larval supply and settlement patterns. Inclusion of diel and ontogenic swimming behaviour increased settlement success of larvae released from inshore areas, regardless of study years. Our study improves understanding of northern shrimp stock‐recruitment relationships, their sensitivity to changing environmental conditions, and spatially non‐homogeneous population decline for bentho‐pelagic species with a long larval phase, which could potentially help improve management strategies.

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Section: Methodsmentioning

confidence: 94%

Assessing connectivity patterns among management units of the Newfoundland and Labrador shrimp population

Corre

Pepin

et al. 2018

Fisheries Oceanography

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“…We then calculated rolling correlations between SST and timing of the winter or spring bloom using 15‐day rolling windows during 10 months before to 60 days after the pulse or bloom. This time frame approximated the shrimp annual reproductive cycle, which starts with ovogenesis the previous spring, and is strongly affected by temperature (Stickney and Perkins, ; Brillon et al ., ; Richards, ;). The rolling windows were constructed relative to the yearday of the peak winter or spring chl‐ a concentration in each year.…”

Section: Methodsmentioning

confidence: 97%

Use of satellite data to identify critical periods for early life survival of northern shrimp in the Gulf of Maine

Richards

O’Reilly

Hyde

2016

Fisheries Oceanography

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The northern shrimp Pandalus borealis is at its southern limit in the Gulf of Maine (GOM), and recruitment success is higher in years with relatively cool water temperature. However, the mechanisms for the temperature effect are not clear. We used rolling window analysis of daily satellite data to identify critical periods for early life survival of the 1998–2012 northern shrimp year‐classes and to investigate the importance of the phenology of the hatch and bloom. Survival was negatively correlated with sea surface temperature (SST) during a 6‐week period around the time of larval emergence (late winter) and during a 4‐week period in late summer when SST and stratification reached annual maxima. Survival was negatively correlated with chlorophyll‐a concentration (chl‐a) during two 5‐week periods centered approximately a month before the hatch midpoint and around the time of settlement to the benthos. A small‐magnitude winter bloom occurred around the time of the hatch in many years, but our results did not reveal a link between survival and bloom‐hatch phenology. The timing of winter and spring blooms were correlated with SST during the preceding 10 months. A survival model including SST and chl‐a during the critical periods explained 73% of the variance in survival. Summer SST increased significantly during the study period; the other critical variables showed no trend. The rolling windows approach revealed sensitive periods in early life history that may not have otherwise been hypothesized, providing a foundation for research towards a greater understanding of processes affecting recruitment.

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“…However, the role of hatch timing cannot be entirely ruled out. The duration of the hatch period has increased since the 1980s (Richards 2012), thus increasing the probability of larvae encountering a favorable window for survival. This could explain the paradox of a boreal species at its southern limit having higher recruitment under warming conditions.…”

Section: Discussionmentioning

confidence: 99%

“…The dock-based measurements were included to represent conditions in nearshore waters where juvenile settlement occurs (Shumway et al 1985). We used average daily SST during the month of March, when the hatch period is reaching completion (Richards 2012) and the early planktonic larval stages are in the water column.…”

Section: Environmental Datamentioning

confidence: 99%

“…For this series, we developed population fecundity indices by applying a size-fecundity relation (estimated from data in Haynes & Wigley 1969) to the annual geometric mean number of spawners per tow of a given length (dorsal carapace length, measured to 0.5 mm). The number of spawners was decremented for the annual portion of natural and fishing mortality that would have occurred before the midpoint of the hatch period (Richards 2012): (4) (5) where i is the year, l is the dorsal carapace length, Fec l is the fecundity at a given length, estimated as Fec l = −0.198l 2 + 128.81l − 17821 (r 2 = 0.76) , N il is the number of spawners at length at mid-point of annual hatch period , N i is the stratified geometric mean number of spawners per tow, M is the natural mortality, assumed to be 0.25 (ASMFC NSTC 2010), P M is the proportion of natural mortality occurring between survey and median hatch date, F is the fishing mortality (from Collie-Sissenwine model, Collie & Sissenwine 1983) (ASMFC NSTC 2010), P F is the proportion of fishing mortality occurring between the survey and median hatch date, estimated from monthly effort statistics (ASMFC NSTC 'Assessment report for the Gulf of Maine northern shrimp-1994' unpubl., 2010), and P l is the proportion at length l.…”

Section: Biological Datamentioning

confidence: 99%

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