# Presentation: 435602

## Research Questions about Climate and Fisheries in the Bering Sea

**Research Questions about Climate and Fisheries in the Bering Sea**

**Gordon H. Kruse**
**University of Alaska Fairbanks**
**School of Fisheries and Ocean Sciences, Juneau Center**
**Juneau, Alaska**

## Importance of the Bering Sea: Fisheries

**Importance of the Bering Sea: Fisheries**

**Catch in EBS would rank in the top 10 fish-producing countries **
**Groundfish harvest is 50% of total U.S. catch **
**Groundfish catches of ****±****1.5 million mt/yr in recent decades**

**Notes:**
Notice the spike in the late 1950’s flatfish YFS,
 turning to pollock in the early 70s prior to the passage of MSA in 76
relatively stable catches at under 2million mt after 1976 

## Important Groundfish Species

**Important Groundfish Species**

**Walleye Pollock***(Theragra chalcogramma)*

**Pacific Cod ***Gadus macrocephalus)*

**Pacific Ocean Perch***(Sebastes alutus)*

**Yellowfin Sole***(Pleuronectes asper)*

##  Groundfish Fisheries

-  **Groundfish Fisheries**

## Crab Fisheries

**Crab Fisheries**

##  Salmon Fisheries

-  **Salmon Fisheries**

##  Herring Fisheries

-  **Herring Fisheries**

##  Ecosystem Context for Fisheries

-  **Ecosystem Context for Fisheries**

## Potential Population-level Responses of Fish to Climate Change

** ****Shifts in geographic distributions and possible establishment of new species**
** ****Changes in seasonal migrations and timing of life history events**
** ****Changes in abundance owing to changes in frequencies of strong recruitment**
** ****Changes in mortality and growth rates**
** ****Changes in predator-prey or competitive interactions among species**
** ****Shifts in pelagic and benthic communities**

## NPRB (2005) Research Needs for Fish and Invertebrates: Specific Needs Relating to Climate Change

**1. Stock assessment research and development**
** ****Incorporation of ecosystem indices in stock assessments**
** ****Spatially explicit stock assessments**
**2. Alternative harvest strategies**
** ****Effects of spatial-temporal disproportionate harvest rates on stock dynamics**
**3. Socio-economic considerations**
** ****Estimation of aesthetic and non-market valuation of ecosystems**

## Research Needs for Fish and Invertebrates:

**4. Reducing catch of unwanted species**
** ****New technologies/methods to monitor and reduce catch of unwanted species**
**5. Causes of perturbations of major species**
** ****Role of natural and human impacts on species declines (e.g., crab, shrimp, Greenland turbot)**
** ****Role of natural and human impacts on species increases (e.g., arrowtooth flounder)**
** ****Migration, inter-mingling, carrying capacity, and ocean survival of salmonids**

**Research Needs for Fish and Invertebrates:**
**Specific Needs Relating to Climate Change**

## Research Needs for Fish and Invertebrates:

**6. Implications of ecosystem change on fishery management**
** ****Develop indicators of ecosystem conditions**
** ****Mechanisms for climate-induced regime shifts of fish/invertebrate communities **
** ****Role of pelagic and benthic forage species on upper trophic dynamics **
** ****Ecosystem effects of large fluctuations in abundance and/or distribution of species (e.g., flatfish, crabs, shrimp, sharks, jellyfish)**** **

**Research Needs for Fish and Invertebrates:**
**Specific Needs Relating to Climate Change**

## Additional Climate-related Priorities Identified by the Scientific and Statistical Committee (2006)

** ****Effects of climate-induced changes in ice and temperatures on fish communities in the Bering Sea**
** ****Effects of dynamics in nutrients and lower trophic levels**
** ****Advancing ecosystem approaches to fisheries management (developing indicators, reference points and models)**

## Methods for Conducting Research on Fish and Invertebrates

** **_**Monitoring**_** – to detect and track changes in ecosystem elements and provide data for modeling and context for process studies**
** **_**Process studies**_** – to identify and understand potentially important rates and processes**
** **_**Retrospective studies**_** – to maximize use of existing long-term observational records**
** **_**Modeling**_** – to synthesize, extrapolate in time/space, test ideas and forecast future scenarios**

**Methods for Conducting Research on Fish and Invertebrates**

## Spatial Variation of Size of Maturity of Walleye Pollock in 2002/2003 

- d

**Notes:**
Logistic regression models were estimated for the 2002/2003 pooled data by area.  A trend occurred with smaller L50 values at higher latitudes for both developing =immature and mature models.  

## Interannual Variation in Maturity

***L******50***** ****Groupings**
**	****Small**** ****-**
**	****89, 91, **
**	****93, 95**
**     ****Medium -**
**     ****02**
**     ****Large *****-***
**	****92, 00, 01**

**Notes:**
Maturity curves were estimated for each NMFS survey year to determine if any interannual variation in maturity exists.  The smallest proportion mature at length and smallest L50 values occurred for 1989 and 1995.  And small L50 values also occurred for 1991 and 1993.  Similar maturity curves and Large L50 values occurred for 1992, 2000, and 2001.  In addition 2002 is similar for proportion mature values less than 0.4, but then shifts to smaller proportions mature for length, therefore the 2002  L50 is smaller than 1992, 2000, and 2001. 

## Shifts in Herring Migration Routes and Overwintering Areas

**Shifts in Herring Migration Routes and Overwintering Areas**

## Variation in Sea Ice and Temperature in Early/late Herring Spawning

**Variation in Sea Ice and Temperature in Early/late Herring Spawning**

## Model of Herring Spawning Timing

**Model of Herring Spawning Timing**

**Observed**

**Predicted**

**Best models involve sea ice concentration in March and April and surface air temperature at Cape Newenham.**

## Crab Recruitment Patterns

**Crab Recruitment Patterns**

## Bristol Bay Red King Crab Recruitment and Aleutian Low Pressure Index

**Bristol Bay Red King Crab Recruitment and Aleutian Low Pressure Index**

**Recruitment may partly relate to decadal regime shifts:**
** ****All strong year classes occurred before 1977 when the Aleutian Low was weak**
** ****Largest year class (1990) in last 20 yr coincided with weak Aleutian Low index during 1989-1991**** **

## Shifts in Crab Distributions

**Shifts in Crab Distributions**

**Northeastward shift of mature females may result in larvae being advected beyond suitable habitats in Bristol Bay. **

## Role of Predation?

**Role of Predation?**

## Slide 24

## Near-bottom T (oC) vs. Groundfish Centers

**Near-bottom T (****o****C) vs. Groundfish Centers**

## Slide 26