Atlantic Herring Conservation

1. Atlantic Herring Conservation Lauren Keyes Yu Kawakami Brigette Jones

2. Herring Stocks http://www.gma.org/herring/biology/default.asp

3. Spawning Sites

4. Larval Dispersal

5. Spawning • Fish migrate from offshore to inshore coastal waters at various locations in the Gulf of Maine to spawn • Females spawn once a year for several years • External fertilization • Egg mats (masses of eggs) laid on the ocean floor

6. Eggs • Egg mats attract variety of predators, contributing to high egg mortality • Eggs hatch 7-10 days after fertilization

7. Larvae • Larvae are 5-7mm long upon hatching • Have attached yolk sac with food supply for +/- 10 days • Gradual switch from yolk to feeding on plankton; critical transition period with extremely high mortality • Only about 1% of larvae survive to become juveniles at 6 months

8. Juveniles • Larvae metamorphose into juveniles in the spring at about 4cm in length • Begin to look more like adults: scales form, body deepens • Do not join adults yet; as adults move inshore to spawn, juveniles move offshore

9. Adults • Juveniles mature into adults at 3-4 years • Measure about 10in • Can live up to 12 years in the Gulf of Maine

10. Migration • Not very well understood, but in general… • Adults migrate against the currents from feeding grounds (offshore) to spawning grounds (inshore) • Larvae drift passively with the currents • Juveniles eventually join the adults

11. Feeding • Herring survive entirely by feeding on plankton, specifically Calanus finmarchicus, the dominant copepod in the Gulf of Maine • Even larval herring eat a lot of larval (naupliar) copepods • Herring distribution depends on copepod distribution • Herring growth rates vary with copepod availability and abundance

12. Predators • Lots of things eat herring…

13. Herring Habitat • Fully marine • Spawn in coastal waters • Depths above 100 meters • Level bottom • Substrates: rocks, cobble, gravel, pebbles, beds of seaweed, fragments of shells • Pelagic larvae • Exposed to currents, tides, and winds • Brit (Juvenile) closer to shore

14. Environmental Factors • Temperature • Salinity • Oxygen • Density • Light

15. Temperature • Spawning happens in temperatures between 10C and 15C • Spawning progresses from north to south • Egg hatching dependent on temperature • 7-10 days • Water temperature determines length of larval stage • 3-11 months (avg: 6 months)

16. Oxygen • Eggs deposited on upper level of egg mat exposed to more oxygen in moving currents • Con: eggs on upper level of egg mat exposed to higher predation

17. Density • Juveniles migrate together in dense schools near surface • Growth dependent on density • Exceeding optimal number decreases growth rates

18. Light • Juveniles (brit) migrate vertically in response to light cycles • Dispersed throughout water column during day • Collect at surface waters at night • Feeding on zooplankton prey

19. We must consider these environmental factors when considering conservation

20. Changes in Abundance • Peak landings in 1968 • 1977 complete collapse on Georges Bank • 6X higher in 1992-98 than in 1968-75 • Lowest from 1971-85 after crash • Increased from 1985 onward

21. Distribution • 3 semi-independent stocks • GoM, Nantucket Shoals, GB • 1970-Continental Shelf from Nantucket to Chesapeake Bay • Highest abundances off Long Island and NJ, Nantucket Shoals • Late 70’s-mid 80’s-most south of Cape Cod • Latitudinal shifts from 39-41oN in Late 60’s to between 40o30’-44o10’N by 1984, back to 41o N since 1989 • Longitudinal shifts from West of 70oW farther East (offshore) through 1986 and then back to 70oW in 1989-1998

22. Catch locations and abundances from Spring bottom trawl data

23. Causes of the Collapse • Excessive fishing mortality • ICNAF (International Commission for the Northwest Atlantic Fisheries) TAC limits routinely set above scientific recommendations for sustainable fishing • Concentration of fishing efforts on spawning areas • Spawning stock and egg and larval decrease • Complete absence of larvae on George’s Bank for 10yrs

24. Mechanisms and Pattern of Recovery • Stepwise recovery because of non-uniform distribution of larvae • Gulf of Maine • Nantucket Shoals • Georges Bank • Progression of larval abundances-colonization • Water circulation patterns support pattern • Recovery of George’s Bank began in 1984 • Full recovery has required nearly 2 decades • Spawning area closures and restrictions on GB beginning in the 1980’s • No offshore landings 1978-94 • Abundances and biomass improved steadily on GB

25. Current Conditions and Recommendations • Continue to prevent concentrated fishing of spawning stock • Possibly rolling closures and/or localized closures of spawning areas • Have recovered to pre-1960’s biomass and abundance • One of top 5 species in abundance and biomass • Annual landings ranged from 60 000 – 100 000 metric tons in early-mid 1990’s • Recovery of Atlantic Herring was possible because of almost totally releasing the populations from fishing pressures, and because larval dispersal between distinct areas was possible