# Presentation: 921123

*Jesús Jurado-Molina*
*School of Fisheries, University of Washington*

*Climate Forcing effects on trophically linked groundfish*
*populations: Implications for Fisheries Management*

- Changes in the Bering Sea

**Notes:**
Mention that we include fishing and climate in single species and multispecies models.

- To apply the single and multispecies forecasting models to assess the effects produced by climate regime shifts and fishing on spawning biomass of some species from the Bering Sea.
- Determine relative roles of fishing, climate regime, and predation in population dynamics

*Objectives*

## Slide 4

*BS* - suitable prey biomass
*S* - suitability coefficient of prey *p *for predator *i*
*R* - annual ration of the predator *i*
*W* - weight at age of prey *p*
*M1-* residual mortality
- M2 - predation mortality

*MSVPA and MSFOR equations*

## Slide 6

## M = M1 + M2
Predator’s annual ration = constant
Average constant suitability coefficients (from MSVPA) 
Other food of predators remains constant 
Suitability coefficients reflect the preferences of the predator, the vulnerability and the availability of the prey and other factors such as the overlapping of predator and prey populations etc.
Suitabilities define the predation interaction dynamics in the forecasting models

- Predator’s annual ration = constant
- Average constant suitability coefficients (from MSVPA)
- Other food of predators remains constant
- Suitability coefficients reflect the preferences of the predator, the vulnerability and the availability of the prey and other factors such as the overlapping of predator and prey populations etc.
- Suitabilities define the predation interaction dynamics in the forecasting models

## El Niño Southern Oscillation (ENSO)
Duration of 2 to 7 years
Global influence  
Pacific Decadal Oscillation (PDO)
 Persistency of 20 to 30 years
 Main influence in the North Pacific and North American sector

- Duration of 2 to 7 years
- Global influence
- Pacific Decadal Oscillation (PDO)
-  Persistency of 20 to 30 years
-  Main influence in the North Pacific and North American sector

*Environmental forcing in the*
*eastern Bering Sea*

- If recruitment success were dependent on a sequence of events, then a semi-permanent shift in ocean conditions would influence only one of several conditions necessary for successful recruitment. Stocks that exhibit this type of recruitment response would show a change in the probability of a strong year class, or a change in the amplitude of strong year classes when they occurred, expressed as a change in the mean level of recruitment (Hollowed and Wooster, 1995) .

*Environmental forcing in*
*the eastern Bering Sea*

- There is a mean recruitment and variance associated with each climate regime
- Recruitment of age-0 individuals takes place in the third quarter
- Recruitment is log-normal distributed
- First scenario: 1977 temperature Regime continues beyond
- Second scenario: There is regime shift in 1989

*Recruitment assumptions*
*associated with climate regimes*

- MSVPA run updated to 1998 data to obtain average suitabilities, average recruitment values and population initial values (1998) for all species.
- ANOVA analysis and comparison of the CV’s for the recruitment from MSVPA for the periods 1979-1988 and 1989-1998
- Multispecies forecasting using the mean and standard deviation of recruitment values associated with the two regime shifts, average suitabilities, initial population values (1998) and four levels of fishing mortality, F30, F40, F50 and no fishing mortality
- Single species forecasting using the corresponding input parameters.
- Spawning biomass ratio selected as indicator of performance:
-     SSB ratio = SSB(2015)/SSB(1998)

*Methods*

- ANOVA and CV’s comparison results for the 1979-1989 and 1989-1998 periods

*Results: recruitment scenarios*

*Results: frequency distribution of spawning *
*biomass ratio of pollock in 2015 (F40)*

*Results: Forecasting of pollock SSB ratio under two climate*
*regimes and F40 level of fishing mortality*

**Notes:**
1.- SSFOR predicts minor  changes in SSB ratio due to climate shifts. 2.- In contrast MSFOR predicts bigger changes for SSB ratio. The 89 shift moved the distribution to the right. 3.- MSFOR results suggest similar probability for a decreasing SSB ratio. However the probability of SSB being smaller than five decreases with the 1889 shift suggesting more increasing possibilities for the SSB ratio of pollock.  For yield ratio, we found the same tendencies as in the SSB ratio case.

*Results: Forecasting of cod SSB ratio under two climate *
*regimes and F40 level of fishing mortality*

**Notes:**
1.- In the case of Pacific cod, both models predicted significant changes when the climates shifts were simulated. 2.- In the single species, both models suggest a bigger probability for a decreasing population for this level of fishing mortality, however the probability of a decreasing population is bigger for the 89 shift. 3.- MSFOR results suggest smaller probability for a decreasing population and consequently the probability of an increasing SSSB is bigger. However the probability of an increasing population is bigger for the 77 shift. In the case of yfs the change of climate regimes did not produce significant changes when the single species model was used. The probability of a decreasing population was around 78%.  The MSFOR produced significant changes in the probability of SSB ratio. The probability of a decreasing population was close to zero,therefore the MSFOR predicts an increasing SSB ratio, being the 77 shift the one producing bigger probabilities for higher SSB ratios.

*Results: effect of two levels of fishing mortality *
*and climate regimes in the forecasting *
*of SSB ratio in 2015*

**Notes:**
In the absence of fishing the probability of a growing SSB ratio increased in the single species forecasting. However, no significant changes due to the implementation of the two climate regimes were observed. The multispecies case is more complex. The multispecies results show that the probability of increase the SSB ratio is bigger for the F40 level  than the no fishing level in both climate regimes. However, when we compare the effect of the climate regimes, we found that the higher probabilities corresponded to the 77 shift. These results suggest that at the F40 level the SSB ratio is more likely to grow than at the no fishing level. The cause of this trend could be the depletion of pollock’s predator(pollock, cod) populations at the F40 level which would result in greater survival for the juvenile pollock. This effect is not predicted by the single species forecasting due to a lack of interactions between species.    	

*Results: effect of two levels of fishing mortality *
*and climate regimes in the forecasting *
*of SSB ratio in 2015*

**Notes:**
The case of Pacific cod is different from the pollock. Even cod juveniles are predated by cod and pollock, the main role of cod is as a predator not a prey. Therefore the juvenile survival is not beneficiated by a depletion of the predators population. The no fishing level produced higher probability for a growing population in both the single and the multispecies models. The results are very similar. Within each model, the 89 climate regime is the one producing higher probability of increase.   

*Results:effect of two levels of fishing mortality *
*and climate regimes in the forecasting *
*of SSB ratio in 2015*

**Notes:**
SSFOR predicts higher probability for an increasing SSB ratio in absence of fishing. There is an effect produced by the climate component. In this model the 89 shift predicts higher probabilities of increasing SSB ratio. For the multispecies case, the no fishing level predicts a high probability of decreasing SSB due to the higher survival of predators, mainly cod, produced by the absence of fishing mortality. The probability of increasing SSB is smaller than the probability of decreasing SSB ratio. In both cases, single species and multispecies the 1989 regime shift produced higher probabilities. 

*Results: temporal trend of the median*
*of SSB ratio of walleye pollock*

*Results: temporal trend of the median*
*of SSB ratio of walleye pollock*

- Climate regime shifts produced an effect comparable to the ones produced by fishing and predation on the species analyzed from the eastern Bering Sea, therefore accurate models for fisheries management will require considering all three factors and their potential interactions.
- To incorporate regime shifts in fisheries management it is necessary to have a better understanding of recruitment behavior during a particular climate regime and a reliable way to identify a potential shift based on biological and/or physical indices.
- Species respond differently to both climate change assumptions and fishing mortality depending on their position on the food web and on their generation time.  Responses are complex and difficult to predict therefore it is necessary to take an even more conservative approach in managing the species with the largest potential variation.

*Conclusions*

- Analysis of additional indicators including predation mortality, total population and catch.
- Inclusion of stochastic Ricker and Beverton and Holt recruitment

*Future tasks*

*The end*