Recovery of the Great Salt Lake Brine Shrimp Population

Transcription

1 Recovery of the Great Salt Lake Brine Shrimp Population By: Brad Marden INVE Aquaculture, Inc. Utah Strategic Alliance, LLC

2 TOPICS Population Dynamics : 1 to 5 years Decline and Recovery: Management and Nature Future Potential for GSL Artemia Population

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4 Goals of USAH Ecological Studies To Provide the Technical Information Necessary for Sustainable Management of the GSL Artemia Fishery Ensure that GSL Artemia population remains both biologically and economically viable. Forecasting and Quantitative Predictions Used for watershed scale management decisions GSL as a model for management worldwide

5 GSL Research Organizations Utah Division of Wildlife Resources (DWR) United States Geological Survey (USGS) Utah State University (USU) INVE Aquaculture/Utah Strategic Alliance

6 Sampling Methods DWR: South Arm: 22 sites, 1 Plankton Net Tow per site, DO, Temp, Salinity, Secchi, Chl A, Phytoplankton North Arm: Currently not sampling USAH South Arm: 12 sites, 2 plankton net tows per site, DO, Temp., Salinity, Secchi, Chl A, Phytoplankton North Arm: 5 sites, Temp. Salinity

7 Population Dynamics: 1996 to /3/95 9/25/95 2/7/96 4/29/96 5/31/96 8/19/96 11/20/96 3/11/97 5/5/97 6/23/97 9/23/97 11/3/97 1/21/98 4/8/98 5/18/98 7/15/98 10/5/98 11/19/98 2/12/99 5/6/99 6/28/99 8/11/99 9/28/99 10/18/99 11/9/99 11/29/99 1/24/00 3/29/00 6/12/00 7/18/00 9/6/00 9/28/00 10/25/00 11/20/00 12/5/00 1/24/01 NAUPLII JUV TOTAL ADULTS DATES NUMBER PER LITER

8 GSL Cyst Density: 1995 to 2001 GSL CYST DENSITY (cysts/liter) Aug-95 Nov-95 May-96 Aug-96 Feb-97 May-97 Sep-97 Dec-97 Apr-98 Jul-98 Nov-98 Mar-99 Jun-99 Sep-99 NUMBER PER LITER Oct-99 Nov-99 Mar-00 Jun-00 Sep-00 Oct-00 Nov-00 Jan-01 DATE

9 GSL Artemia: Sex Ratios Sex Ratio: Female:Male Aug-95 Dec-95 Apr-96 Aug-96 Dec-96 Apr-97 Aug-97 Dec-97 Apr-98 Aug-98 Dec-98 Apr-99 Aug-99 Dec-99 Apr-00 Aug-00 Dec-00 DATE

10 GSL South Arm Salinity: 1986 to Parts per Thousand Year

11 Phytoplankton Trends 1996 to 2001 Chlorophyte Diatom Other Relative Abundance 100% 80% 60% 40% 20% 0% Year

12 Life History Traits and Population Dynamics Onset of hatching in spring: Early to mid-march (can be as early as the end of February) First hatching event: GSL temperature generally above 7 degrees Centigrade. Days to maturity:42 to 56 days First cohort: No correlation with summer population size. Three to five generations: Probably a multiplicity of overlapping generations. Shift to oviparity in July. Final demise of population in late November or early December (water temperature generally below 4 degrees Centigrade) Female to male sex ratio: 0.6 to 1.2 Population decline in 1997 to 1999 followed by robust recovery in i 2000 and 2001 coincides with changes in salinity.

13 Objectives for 2001 Improve accuracy of population assessments-- --impression that size and timing of each age-class peak were not correctly measured Enhance predictive capabilities (modeling of cyst production) Determine most significant biotic and abiotic influences on population dynamics (especially phytoplankton) not entirely convinced salinity alone is most influential factor. Expand the scope (added phytoplankton and Chl A) and increase the frequency of USAH sampling program (weekly sampling) Turn-around time of all counts within 3 days

14 Population Dynamics 2001 Cysts and Nauplii Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan-02 Nauplii Meta-nauplii Total Nauplii True Cysts Count per Liter DATE

15 Population Dynamics, 2001 Juveniles, Pre-Adults, Adults Juveniles Pre-Adults Total Adults 10-Dec Dec Jan Jan Feb Feb Mar Mar Apr Apr Apr May May Jun Jun Jul Jul Aug Aug Sep Sep Sep Oct Oct Nov Nov Dec Dec Jan-02 Number per Liter Date

16 Female Reproduction, Apr May May Jun Jun Jul Jul Aug-01 7-Sep Sep Oct Oct Nov-01 6-Dec Dec-01 Counts per cubic meter Females Gravid F. F+ Embryos F+Cysts F+Nauplii DATE

17 6-Nov Nov Dec-01 2-Jan-02 Brood Sizes, 2001 Embryo per F Cysts per F Nauplii per F Apr-01 8-May May-01 6-Jun Jun-01 5-Jul Jul-01 6-Aug Aug Sep-01 3-Oct Oct-01 Count DATE

18 Reproductive Mode, % 90.0% 80.0% 70.0% 60.0% 50.0% 40.0% 30.0% 20.0% 10.0% 0.0% 8-May May-01 6-Jun Jun 5-Jul 23-Jul-01 6-Aug Aug Sep-01 3-Oct Oct-01 6-Nov Nov Dec-01 2-Jan-02 Percentage of All Gravid Females %FE/Gravid F %FC/Gravid F %FN/Gravid F DATE

19 Relative Abundance of GSL phytoplankton Cyanophytes Chlorophytes Diatoms Unknown 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 22-Aug Sep Sep Oct-01 6-Nov Nov-01 4-Dec Dec-01 9-Jan-02

20 Sex Ratios, 2001 Female: Male /20/01 4/3/01 4/17/01 5/1/01 5/15/01 5/29/01 6/12/01 6/26/01 7/10/01 7/24/01 8/7/01 8/21/01 9/4/01 9/18/01 10/2/01 10/16/01 10/30/01 11/13/01 11/27/01 12/11/01 12/25/01 DATE Ratio Female:Male

21 Spatial Distribution of Cysts in the Water Column: AUGUST SEPTEMBER OCTOBER DECEMBER JANUARY Cysts Per Liter 8 9 DEPTH (m) MONTH

22 Results of 2001 Sampling Changes Greater resolution in identifying peak densities of Artemia age-classes. Accurate predictions of peak cyst density (June predict =87c/l; Actual=87 c/l) and harvest quantities (September = 8269 MT; Actual = 8312 MT) More defined details of reproductive output-- --may be useful to examine relationship with environmental characteristics. More representative estimation of phytoplankton dynamics. Temporal influence on spatial distribution of cysts in the water column. Cyst or egg brood sizes are similar over time. The sex ratio for 2001 was substantially different than the previous 5 years.

23 Population Recovery: Good Management or Normal Fluctuations? 2000 and 2001 were both well below normal in precipitation

24 Industry and Management Decisions Voluntary abstention by industry from harvesting on South Arm in 1999 Dredging operation to increase bi-directional flow of heavy brines from North to South Continuing to regulate industry using minimum acceptable cyst density.

25 COMPARISON OF BOLSHOE YARAVOE AND GSL Brine Shrimp Industry: Demonstrated capability to harvest more than 500 MT per day. THE GREAT SALT LAKE GENT BELGIUM APRIL 24, 2001

26 Future of the GSL Artemia Population Favorable conditions in winter 2002 El Nino-- --Not likely factor in 2002 Spring hatching conditions will be critical

27 Nutrient dynamics in GSL Detailed bathymetry study Genetic characterization: One species or more? North Arm Artemia: Life History of the fittest 265 ppt and still reproducing? RESEARCH NEEDS

28 Questions?