# Presentation: 338575

## Wind-Driven Transport Indices for Cod and Haddock Recruitment on Georges Bank

**David Mountain, Jim Manning, Jon Brodziak, Loretta O’Brien**

## Wind-Driven Transport Indices for Cod and Haddock Recruitment on Georges Bank

**David Mountain, Jim Manning, Jon Brodziak, Loretta O’Brien**

**Outline:**
**     ****1. Background  (why we even thought of doing this)**
**     ****2. What we did**
**     ****3. Results**
**     ****4. Why it doesn’t work**
**     ****5. What we learned (that may be even better!)**

## Egg Hatching to Recruitment

**1.  GLOBEC Monthly Surveys**
**     ****Jan – June, 1995-1999**
**2.  Cod and Haddock eggs staged**
**Annual estimates of **
**	****  ****a)  eggs spawned**
**	****  ****b)  egg hatched**
**         ****c)  egg mortality**

**Cod early stage eggs,  February 1997**

**Egg Hatching to Recruitment**
**Cod:****	****       R****2**** = 0.8  (p<0.04)**
**Haddock:     R****2**** = 0.5  (p<0.18)**

**GLOBEC Georges Bank Program**

## So..... what determines egg mortality?

**Seasonal Egg Mortality Rate (%/day)**

**Variation in hatching due mainly to variation in egg mortality**

**So****..... what determines egg mortality?**

|  | Cod | Haddock |
| --- | --- | --- |
| 1995 | 13.7 | 12.0 |
| 1996 | 12.2 | 11.3 |
| 1997 | 20.4 | 13.4 |
| 1998 | 9.9 | 7.8 |
| 1999 | 15.4 | 9.9 |

## Wind driven transport off Georges Bank!

**Wind driven transport off Georges Bank!**

**Simple transport model:**
**    ****climatological flow field**
**      ****(from hydrodynamic model)**
**                  ****+**
**    ****time-dependent Ekman current**

**For each year:**
**1.  Use early egg distributions (10 day periods over the season)**
**2.  Track egg particles for 17 days (time to hatching)**
**3.  If cross 200m isobath on southern flank of the bank, assumed lost**
**4.  Sum for the season and determine the mortality (loss) rate.**

## Run the model

**Cod**

**Haddock**

**Model Mortality (ppd)**

**Observed Mortality (ppd)**

**R****2**** = 0.7  (p < 0.18)**

**R****2**** = 0.5  (p < 0.30)**

**Run the model**
**Modeled mortality similar to observed**
**Regression slopes ~1**

**[ Chase did this for haddock**
**  ****(1931 – 1950) using SE winds**
**  ****with R****2**** ~ 0.5  for recruitment ]**

## The proposed project:

**The proposed project:**
**         ****SSB         spawning          egg mortality        hatching        recruitment**
**                             ****SSB                   Wind                   recruitment**
**    ****Take longer time series and see if index for recruitment could be developed:**

**Assumes:**
**    ****SSB is a proxy for egg production  (fecundity is constant)**
**    ****Spatial/temporal egg distribution constant  (use GLOBEC distribution)**
**    ****Egg mortality represented by wind-driven model**
**    ****Hatching is a proxy for recruitment (larval/juvenile survival is constant)**

**Basically, to give a ‘heads up’ for higher or lower R than expected**

## So, run the model, 1979 to 2003:

**(2003, 788)**

**So, run the model, 1979 to 2003:**
**              **** ****(SSB        wind-driven transport       egg survival)**
**Compare Recruit Index vs actual Recruitment**
**Not very good....!!**

**Haddock**

**Cod**

## Why?

-      **Using years with egg data (spawn, mortality, hatch):**
-         **  ****SSB                         spawning                       not so good**
**          ****Obs mortality         model mortality             not so good**
**          ****Hatching                 recruitment                   ...interesting!**

**(Have egg spawning, hatching and mortality estimates for 1979-1987 & 1995-1999)**

## Egg hatching to Recruitment

**Egg hatching to Recruitment**

**MARMAP  (1980’s)**
**GLOBEC   (1995-1999)**

**Haddock**

**Cod**

**Hatching  (x10****-12****)**

**Recruitment (x10****-6****)**

**Haddock:**
**    ****About 3 times recruits/egg**
**    ****in 1990’s as in 1980’s**
**Cod:**
**    ****Just the reverse**

## Combining Cod and Haddock

**Hatching  (x10****-12****)**

**Recruitment (x10****-6****)**

**Combining Cod and Haddock**

**Consistent pattern **
**     ****for both periods**
**‘****order’ vs ‘scatter’**
**Densty dependence?**
**Consistent ‘Egg to R’,**
**Just shift between species**
**In the different periods.**

## So, what else was going on?

**Salinity Anomaly on Georges Bank**

**Zoo Community Structure**
**(Kane 2007)**

**So, what else was going on?**

**Low salinity in 1990’s**

**Change in zoo community**

## So, what else was going on?

**Salinity Anomaly on Georges Bank**

**Zoo Community Structure**
**(Kane 2007)**

**So, what else was going on?**

**1990’s:**
**- Low salinity**
**- Smaller copepods**
**- Haddock favored over cod**

## So, what else was going on?

**Salinity Anomaly on Georges Bank**

**Zoo Community Structure**
**(Kane 2007)**

**So, what else was going on?**

**1990’s:**
**- Low salinity**
**- Smaller copepods**
**- Haddock favored over cod**

**A ‘FATE’ connection?**

## Recruits/hatched egg    vs   Zoo Index

**Recruits/hatched egg    vs   Zoo Index**

**Haddock**

**Cod**

**Not just decade – to – decade**
**Create ‘Zoo index’**
**Relationship over the whole period**

## So, where did the low salinity come from?

**Salinity Anomaly &**
** ****Labrador Current Transport**

**So, where did the low salinity come from?**

**High latitude**
**        **** ****The Arctic?**

**A ‘Climate Change’ connection?**

## So ......

**So ......**
**      ****Initial project didn’t work – too much variability at all steps**
**But .....**
**      ****Have a new, FATE related, issue to pursue!**
**Session at 2008 Ocean Sciences:**
**074   “Influence of Recent Changes in the Arctic **
**           ****on Sub-arctic and Mid-latitude Marine Ecosystems”**

## Slide 18

## Slide 19

## Test of the Ekman current approach

**Test of the Ekman current approach**
**Using satellite tracked drifters, drogued at 10m depth**
**Three examples where drift track changed direction with a major wind event.**
**Red (‘D’)**** is drifter;  ****Green (‘C’)**** is climatology;  Blue (‘W’) is climatology + Ekman**

## Slide 21

## (2003, 6)

**(2003, 6)**

## For an operational index, can only use parameters that will be available

**The proposed index depends on:**
**     ****SSB  -  which can be estimated**
**     ****Wind measurements -  which are available**
**To test this:**
**    ****Have SSB and R from VPA’s**
**    ****Have egg spawning, hatching and mortality estimates for 1979-1987**
**    ****Have wind data from NDBC buoys and from NCEP**
**    ****Use mean early egg distributions (10-day cohorts) from GLOBEC**

**Basically, to give a ‘heads up’ for higher or lower R than expected**