# Presentation: 194312

## Fisheries Implications of Freshwater Diversions

**Fisheries Implications of Freshwater Diversions**

- Coastal Wetland Planning, Preservation, and Restoration Act (CWPPRA)
- Outreach Committee Topic Series
- December 2001

## Floods, Fisheries, and Diversions?

**Case Study : Caernarvon**

**Floods, Fisheries, and Diversions?**

**What does history have to say about floods and fisheries? Levees and landings?**

**What is the situation regarding land loss             in coastal Louisiana?**

## Slide 3

## Salt + water ≠ fish !

**Floods and Fisheries**

**Alluvial fertilization **

**Location, location, location**

**LA leads lower 48 in fisheries landings**

**Salt + water ****≠**** fish !**

##  “...a crevasse in reality results in the restoration of our wetlands ...the effect of a crevasse is akin to the cultivation and fertilization of farm lands and might be termed wholesale aquaculture.”

- Percy Viosca, Jr. (1927)
- American Fisheries Society

## The Great Flood of 1927

## Fortification of Levee System

**Fortification of Levee System**

## 160-200 million metric tons a year

## Net Result?

-   25-30 square miles per year

-   1 acre of land every 24 minutes

**Louisiana has lost 1000 square miles of coastal wetlands in the past century.**

## What’s at stake?

***What’s at stake?***

## How have our fisheries been affected by all this land loss?

## Who needs habitat?

**(million pounds)**

**1930**

**1935**

**1940**

**1945**

**1950**

**1955**

**1960**

**1965**

**1970**

**1975**

**1980**

**1990**

**1995**

**1985**

**Year**

_***Who needs habitat?***_
**Louisiana Commercial Fisheries Landings**

## Slide 13

## Land-Water Interface Length                 for Coastal Louisiana

**Land-Water Interface Length                 for Coastal Louisiana**

- (Source: Browder et al.1985, 1989)

**Notes:**
Is deterioration sustainable? Consider this graphic produced by Browder in 1989: The marsh’s land-to-water interface was plotted by Browder et al using historical and simulated rates of coastal land loss - what they found was that ther is some threshhold where eventually this interface reaches a theoretical maximum – and then begins to decline.  Browder predicted this maximum would be reached somehwere by the year 2002 – and that by 2050 we’d be in a precipitous decline.

This is a prediction that does not bode well for future fisheries production.  Clearly, “edge” or “Marsh Interface” is a main contributor to fisheries productivity. Strong correlations have been reported in scientific studies (eluding to Turner here) linking high coastal fisheries production with high amounts of coastal wetland area

So are there any limits at all? In the long run YES! – ultimately, fisheries production will be limited by marsh interface – and I know of no technological innovation that can overcome this loss of habitat - other than coastal  restoration. 

## Will the fishing always be great?

***  ******What is sustaining La’s***
***   ******coastal fisheries:*****                                   **
_**   **__**Alluviation or Deterioration?**_

**  ****Are we consuming**
**    ****interest or principle?**

***Will the fishing always be great?***

## Coast 2050:                                                    Toward a Sustainable Coastal Louisiana

**Coast 2050:*****                                                    ******Toward a Sustainable Coastal Louisiana***

**Local, state, federal consensus effort 1997-98**

**77 ecosystem restoration strategies**

**Restore 500,000 acres over next 50 years**

**Estimated price tag:  $14 Billion**

## Coast 2050:                                                    Toward a Sustainable Coastal Louisiana

**Coast 2050:*****                                                    ******Toward a Sustainable Coastal Louisiana***

## Slide 18

## Slide 19

## Slide 20

## Caernarvon

** ****Construction 1988 - 1991**

** ****$26 million in construction costs (25% state) **

**Enhancement of marsh vegetation, fisheries enhancement, and reduction of marsh loss**

**  ****Post Construction Monitoring 1991-94**

## Slide 22

**Notes:**
Overall, post-diversion catch rates increased at sampling stations for 7 of the 8 fin fish species monitored during the first 3 years of post operation monitoring at Carenarvon . Some of this increase may have been caused by a rebound of stocks following the severe freeze of December 1989.  Sampled fishes included Sheepshead, Atlantic Croaker, Spot, Gulf Menhaden, red and black drum, sand trout and speckled trout.

## Slide 23

**Notes:**
Fisheries-independent sampling of Speckled trout depicted the only post construction decline and commercial landings of specks were also down in the study region compared to the statewide average.  However, some of this difference has been attributed to the partial switching of commercial effort to the mullet fishery (Mugil cephalus).  Later in the 1990s the ban on commercial gill nets would further reduce commercial landings.  But - from a recreational standpoint, charter boat operators targeting spotted seatrout in the area have reported displacement (rather than reduction) of the speck fishery since the freshwater diversion began.  At least one spokesman (Nash Roberts) has indicated that overall recreational catch has not been affected detrimentally.  For the remaining commercial species, commercial landings data from finfish dealers in the Delacroix/Ysclosky area showed no pre/post statistical difference in comparison to the control site, Terrebonne Parish. 

## Intermediate to Brackish  Marsh Boundary

**Intermediate to Brackish  Marsh Boundary**

## Finfish

**Finfish**

_**Post-diversion**_

**Notes:**
Though not an officially monitored species at Caernarvon, there has been tremendous rebound of the largemouth bass fishery that once existed in the region.  The resurgence of this fishery has been documented in national media and is partly credited as the reason why the Bass Anglers Sportsman’s Society (B.A.S.S) selected New Orleans in 1999 and 2001 as host city for its premier fishing tournament.  This picture from one of the many local guides services that have sprung up in the area and offer recreational fishing opportunities for largemouth bass in some of the same waters where redfish and speckled trout are found.

## Slide 26

**Notes:**
Moving on to commercial crustaceans – the effects of Caernarvon have shown:

Blue Crab:  (Callinectes sapidus)        No significant spatial redistribution in sampling catch and Sampling data inconclusive with respect to the diversion and salinity.  Additionally there has been no significant catch reduction reported at buyers and landings cycled upwards or downwards with state landings.

White Shrimp (Liptopenaeus setiferus) some minor displacement (spatial redistribution) was observed in white shrimp sampling depending on gear type.  Catch per unit effort (CPUE) was either equal or slightly higher for White Shrimp during post-construction. However, commercial landings were not correlated with state landings during pre-construction period so it’s difficult to draw conclusions based on the first 3-year period alone.

Brown Shrimp – brown shrimp did show spatial redistribution (displacement) in sampling during the first three years post-construction and CPUE was significantly lower during  during post-construction  for certain gear types.  However, data on commercial landings showed no detectable post-construction effect and have cycled upwards or downwards in accordance to state landings.  The most definitive statement we can make about Brown shrimp in the wake of Caernarvon is that there has merely been a seaward shift (displacement) in optimal harvest zone, which is consistent with what we know as the preference for higher salinities by adult brown shrimp.

## Slide 27

**Notes:**
(activate arrow) so...the take home message when you thing about this circular migration that we’ve all seen is this...(activate red pie slice) – the estuarine habitat that supports these species is often very, very, low salinities:  0.2 – 5ppt for juvenile and post larval brown shrimp, white shrimp, and blue crabs.  In other words, freshwater inputs – to the extent that they help sustain low salinity habitats – are beneficial for commercial crustaceans.

## Slide 28

## Slide 29

**Notes:**
To really understand the oyster conflict at Caernarvon – you need to know the difference between the private and public grounds.  

## Slide 30

**Notes:**
Monitoring data depicted high mortality for oysters stations nearest the structure and the river but dockside interviews indicate dramatic increase in oyster production during post-construction. Clearly what we have seen at Caernarvon is the displacement and enhancement pattern documented by Viosca  over 75 years ago. 

## Slide 31

## Slide 32

**Notes:**
Consider oyster production in the Breton sound befor the Caernarvon re-introduction (animate first half of bar graph) – then afterwards (second half animated) we can see that Caernarvon has clearly been successful in enhancing seed and sack oyster pruction on the outside reefs – which is one of the main objectives of the project.

## Slide 33

**Notes:**
So who was Percy Visoca?  Well, 75 years ago he was the Director of Fisheries for the Commission that would eventually become the LDWF.  In 1927, the same year of the Great Flood, he discussed the fisheries effects of a crevasse in a national address to the American Fisheries Society....read the first quote

Percy also seem to have handle on the issue of oyster displacement – something we seem to be struggling with at caernarvon...read second qoute....pause for effect  - next slide

## Slide 34

## Slide 35

## Slide 36

**Notes:**
To summarize, if we look to history – both geologic and 20th century history, we see that our position as a national leader in seafood productivity is not because we have clear salty water – but because of the alluvial fertilization and habitat building that the Mississippi river has provided for so long.  
But in the past century this system has changed dramatically  due to coastal land loss - largely because of antidiversions like the levee system and the MRGO.  Though fisheries landings data indicate a steady increase, there is some indication that much of this productivity is now being driven by deterioration, rather than alluviation.

As we divert...or Re-introduce the earth sweet waters of Old mad River...whethor it be at Caernarvon, Davis Pond, or Pontchartrai, we need to remember that fisheries will be affected..but in different ways in the short run and in the long run.  Clearly the salinity and fisheries assembalges of the Ponchartrain Basin can be significantly affected by River Re-introductions – as they have likely been affected by antidiversions. 

Though not all respond the same way to freshwater (in fact it’s highly species-specific),  given enough time we typically see a pattern reduction, displacement, and ultimately enhancement. Of course this all depends on the scale of the reintroduction, its location, environmental variables, and operational management within and across seasons.  The crux of the matter is that this management  (at least at caernarvon) tends to become more driven by short-run considerations than by long-run considerations.