# Presentation: 050214

## All in the Family (?)  

- All in the Family (?)
- Diversity of habitat use in anguillicolid eels
- Karin E. Limburg

## Recall Paul Angermeier’s depiction of eel life history as a complex set of phases...much confusion, uncertainty.

- Turns out that eels do display a broad repertoire of habitat use.  How we know this now is through studies of otoliths...
- First, basics
- Second, Swedish example
- Third, comparisons betw. 3 anguillid spp.

## Otoliths (earstones) are increasingly used as natural tags of fish life history

- Part of hearing & balance system
- Grow as fish grows, with **daily** and **annual** increments
- Aragonite (CaCO3) precipitated on protein matrix – entrains other elements

## Otolith microconstituents increasingly used as natural tags

- Sr is particularly useful to track diadromy
- Sr, like Ca, is an alkaline earth element with similar ionic radius – can substitute for Ca in the otolith’s aragonite
- Srsea generally >> Srfresh
- Can use Sr:Ca ratios to trace salinity histories of fish

## Measuring Sr in otoliths

- Microanalytic techniques
- Wavelength dispersive electron microprobe (WDS), can make point transects on the order of microns

## Nuclear microprobe combined with proton-induced x-ray emission analysis (PIXE)

- - higher resolution technique
-  able to measure multiple             	elements at ppm levels
-  can map entire otoliths 	quickly

## Q: Do these fish contribute to the spawning stock, or just to “put and take” ???

-  Catadromous
-  Highest value-added fishery
-  Catches of silver eels in 	Baltic Sea declining since 60’s

**Q: Do these fish contribute to the spawning stock, or just to “put and take” ???**

- European eel,
*Anguilla anguilla*

## What do Baltic eels do? Hypotheses

**Westin ’90**: stocked eels don’t swim in, so they can’t smell their way out – instead, they get “lost” in southern Baltic following thermal gradients

**Sved****ä****ng & Wickstr****ö****m ****’****97**: no correlation between silver eel fat and maturity indexes – silver eels may halt migration and revert to feeding, to “bulk up” for the big swim

## What do Baltic eels do?

**What do Baltic eels do?**

**Tsukamoto et al. ’98: **catadromous eels do not contribute genes to spawning stock

**If we can trace the movement of eels, and collect them leaving or “lost” in the Baltic, we should be able to test all three hypotheses **

## Slide 10

## Salinity history recorded in a silver eel otolith

**Salinity history recorded in a silver eel otolith**

## Slide 12

## Habitat use categories

**Habitat use categories**

-  MB = marine  brackish

-  B = brackish

-  CM = “complex migration”  	betw. marine and brackish

-  CAT = catadromous

-  M = 100% marine

## Does the proportion of wild to stocked silver eels differ by where they were caught?

## How does lipid content vary among presumably stocked eels?

## What do differential fat reserves imply for migrating to the Sargasso, 6000+ km away?

## Comparing among 3 species

- (Daverat et al., MEPS *in press*)

## Comparing among 3 species

| Ecosystem | Ref | Species | Latitude | Water temperature range | Salinity range |
| --- | --- | --- | --- | --- | --- |
| Sweden and Denmark, Baltic exit | Limburg et al 2003 | A. anguilla | 55°N | 2 to 18°C | 0 to 25 |
| France, Gironde River basin | Daverat & Tomas |  | 44°N | 7 to 24°C | 0 to 35 |
| Taiwan, Kaoping River basin | Tzeng et al 2002 | A japonica | 22°N | 18 to 30°C | 0 to 32 |
| Japan, Tone and Fukui river basins | Tsukamoto & Arai 2001  |  | 30-37°N | 6 to 23°C | 0 to 29 |
| Japan, Mikawa Bay connected to 3 rivers | Tzeng et al 2003 |  | 34°N | 8 to 28 °C | 25 to 33 |
| China, Pearl River |  |  |  | 0 |  |
| United States, Hudson River basin | Morrison et al 2003 | A. rostrata | 42°N | 0 to 27°C | 0 to 24 |
| Canada, East River | Jessop et al 2002 |  | 45°N | -1 to 17°C | 0 to 32 |
| Canada, St Jean estuary | Thibault et al. unpublished data |  | 48°N | -0,3 to 24°C  | 1 to 28 |
| Canada, St Jean River and Sirois Lake |  |  | 0 to 24°C covered with ice in winter) | 0 |  |

## Stable brackish (female from Kullen) 

- Stable brackish (female from Kullen)

- (H. Wickström)

## American eel, St Jean Estuary and Sirois Lake

- (Gaspé Peninsula)

## European eel,

- Gironde
- estuary

## Slide 22

## Japanese eel,

- Kaoping River,
- Taiwan

## When do I leave?

| Reference | Life history | Year of shift |
| --- | --- | --- |
| Thibault et al. unpublished data | Residence in brackish site then shift to freshwater habitat | < 6+ |
|  | Residence in fresh water then shift to brackish water | < 6+ |
| (Tzeng et al. 2002) | Residence in fresh water then shift to brackish water | < 5+ |
|  | Two years in fresh water, one in brackish and then residence in fresh water | 3+ |
| Daverat & Tomas | Residence in fresh water then shift to brackish water | < 5+ |
| (Morrison et al. 2003) | Residence in fresh water then shift to brackish water | < 5+ |

## A. anguilla

* *

***A. japonica***

***A. rostrata***

- Baltic Sea exit (silver eels)

- Kaoping estuary (yellow eels)

- Hudson River estuary (yellow eels)

- Gironde estuary (yellow eels)

- Mikawa Bay (silver eels)

- St Jean estuary (yellow &
- silver eels)

## Eel habitat use and Latitude