Journal of Aquaculture Development

fa تنوع و تراکم زئو‌پلانکتو‌ن‌های مزارع پرورش میگوی پا سفید غربی (Litoppenaeus vannamei) در سایت میگوی گمیشان، استان گلستان Study on the Diversity and Abundance of Zooplankton in western white shrimp (Litopenaeus vannamei) Farms at the Gomishan Shrimp Site تخصصي Special پژوهشي Research <div style="text-align: justify;">      این پژوهش از خرداد تا مهر 1402 در سایت پرورش میگوی پا سفید غربی (Litoppenaeus vannamei) گمیشان (استان گلستان) به‌منظور بررسی تنوع زئوپلانکتون‌ها انجام شد. برای این منظور سه مزرعه و از هر مزرعه سه استخر از لاین 2 انتخاب شد. نمونه‌برداری زئوپلانکتون‌ها بوسیله تور پلانکتون‌گیر با چشمه تور 60 میکرون و جهت اندازه‌گیری پارامترهای فیزیکوشیمیایی آب از دستگاه پرتابل HACH مدل HLC40 استفاده شد. زئوپلانکتون‌های شناسایی‌شده شامل Foraminifera, Copepoda, Nauplii of Copepod, free-living Nematodes, Polychaete larvae, juvenile larvae of the worm Streblospio gynobranchiata, Gammaridae, insect larvae Ephydra sp.,  و  Rotiferaبودند. بیشترین فراوانی زئوپلانکتون‌ها در اوایل مرداد مشاهده شد. Copepoda بیشترین فراوانی را در تمام مزارع داشتند. میزان آمونیاک بین 11/0 و  02/0 میلیگرم بر لیتر، میزان نیترات بین  68/0و 07/0 میلیگرم بر لیتر، میزان pH  بین 73/8 –1/8 ، TDS بین 63/18 تا 45/29،  شفافیت بین41 و160سانتیمتر، شوری بین 8/18 تا 2/31 گرم بر لیتر، اکسیژن بین  2/6 تا  66/8 میلیگرم در لیتر و دما بین41/22 تا 81/29  درجه سانتیگراد اندازهگیری و ثبت گردید. نتایج بررسی همبستگی نشان داد که فراوانی کل زئوپلانکتونها با شوری همبستگی خطی معکوس در سطح 1% (474/0-r=) داشت. کمترین و بیشترین شاخص سمیپسون 41/0 و 91/0، شاخص شانون بین 14/0 و 1، شاخص ایونس بین 63/0 و 94/0 و شاخص مارگالف بین 17/0 و 76/0 متغیر بود. شاخص‌های تنوع نشان داد که مزارع از نظر غنای گونه‌ای فقیر بودند، ولی کاهش ضریب تبدیل در استخرهای پرورش نشاندهنده مصرف غذای زنده در کنار غذای دستی بود.  </div> Introduction: Understanding pond structure and performance is essential to enhancing shrimp production efficiency. A critical yet often overlooked factor is the role of natural food sources—such as microalgae, benthos, and zooplankton—in crustacean nutrition (Tacon, 1987; Martinez Cordova et al., 1998). Multiple studies confirm that shrimp, including L. vannamei, prefer live pond organisms over supplemental feed (Hena et al., 2011). Research by Bakhtiari et al. (2012) and Kavyani et al. (2012) identified copepods, rotifers, decapod larvae, and sergestids as dominant planktonic groups in western white shrimp ponds. Shrimp rely on detritus, phyto- and zooplankton, and macrobenthos throughout their life cycle, alongside formulated feed (Farhadian et al., 2014). Moss (2002) demonstrated that up to 53–77% of vannamei growth in non-fed ponds stems from naturally occurring organisms, including plankton and benthos. This study therefore investigates zooplankton diversity and abundance in shrimp ponds and their relationships with physicochemical parameters to optimize natural productivity. Materials and Methods: Fieldwork was conducted during the Litopenaeus vannamei cultivation cycle (110 days; June  to September, 2023) across three 1.2-ha ponds (one per farm: Farms 4, 7, and 10) at the Gomishan Shrimp Farming Site, Golestan Province. Water quality parameters—air and water temperature, pH, dissolved oxygen, oxygen saturation, salinity, TDS, and EC—were measured weekly using a Hach HLC40 portable meter; water transparency was assessed with a Secchi disk. Ammonia and nitrate concentrations were analyzed via Palintest kits. Zooplankton samples (30 L per pond) were collected biweekly from four standardized points using a 60-μm mesh net and fixed in 4% formalin (1 L containers). In the lab, subsamples were identified and counted under a microscope following Tomas (1997) and Barnes (1978). Pearson’s correlation assessed links between zooplankton abundance and physicochemical variables. Biodiversity indices (Simpson, Shannon-Wiener, Pielou’s Evenness, Margalef) were calculated using PAST 3; all statistical analyses were performed in IBM SPSS v22.0. Results and Discussion: In this study, the zooplankton assemblage comprised foraminiferans, copepods, copepod nauplii, various free-living nematodes, larvae and juvenile worms of Streblospio gynobranchiata, gammarids, insect larvae of Ephydra sp., and occasionally rotifers. Copepods were overwhelmingly dominant across all farms and sampling dates, reaching a peak abundance of 151.05 individuals per liter in mid-July, representing the highest density recorded throughout the entire cultivation period. No statistically significant differences were observed among farms at any sampling time for physicochemical parameters including temperature, pH, dissolved oxygen, salinity, TDS, and water transparency. However, salinity and TDS showed a consistent upward trend from the late June to early September, likely due to evaporation and limited water exchange. No significant inter-farm differences were detected in ammonia or nitrate concentrations at corresponding time points; yet, nitrate levels increased significantly by the end of the culture cycle compared to initial values, while ammonia concentrations remained relatively stable—indicating active nitrification within the ponds. Biodiversity indices revealed pronounced temporal changes: Simpson’s Index: Increased from 0.41 (early cycle) to 0.91 (late cycle), reflecting strong dominance by a few taxa (mainly copepods). Shannon-Wiener Index: Declined sharply from 1.00 (early) to 0.14 (late), indicating severe loss of species richness. Pielou’s Evenness Index: Ranged between 0.63 and 0.94, showing moderate decline toward season end. Margalef’s Richness Index: Decreased from 0.76 (early) to 0.17 (late), confirming substantial reduction in species diversity over time.These results indicate that although total zooplankton abundance remained high due to copepod dominance, species richness and community evenness declined markedly during the cultivation cycle, suggesting progressive homogenization and ecological simplification of the pond ecosystem.Correlation analysis between total zooplankton abundance and environmental variables revealed a moderate negative correlation with salinity (r = –0.474), but no significant correlations with temperature, pH, dissolved oxygen, TDS, EC, ammonia, or nitrate. A moderate negative correlation was also found between salinity and dissolved oxygen (r = –0.438), and a weak positive correlation between salinity and pH (r = 0.302). The findings confirm that Litopenaeus vannamei relies substantially on natural food sources including zooplankton, detritus, phytoplankton, and benthos to meet its nutritional requirements, contributing to the low FCR values (0.52–0.77) observed in this study. Farhadian et al. (2014) reported similar patterns, emphasizing that shrimp utilize live food resources throughout their life stages, with consumption rates dependent on age and availability. Bakhtiari et al. (2012) identified copepods, rotifers, decapod larvae, sergestids, and crustacean larvae as the dominant components of zooplankton communities in Dalvar shrimp ponds. Kavyani et al. (2012), studying western white shrimp farms in Bushehr, found rotifers to be the most abundant group among 13 identified animal plankton genera. Conclusion: According to the results of this study, copepods constituted the majority of the zooplankton community, while the low density of rotifers and the absence of cladocera could be due to high salinity. Biological indices showed that the farms were poor in terms of species richness. This is probably due to the use of fine filters and unfavorable conditions at the end of the culture season such as increased salinity, organic matter and decreased temperature. میگوی پاسفید غربی, سایت میگوی گمیشان, پرورش میگو, خصوصیات فیزیکی و شیمیایی Gomishan shrimp site, physical and chemical characteristics, Litopenaeus vannamei 106 120 http://aqudev.lahijan.iau.ir/browse.php?a_code=A-10-151-5&slc_lang=fa&sid=1 Abbasali Aghaei Moghaddam1 عباسعلی آقایی مقدم1 aghaeifishery@gmail.com 100319475328460012307 100319475328460012307 Yes 1-Inland Waters Aquatics Resources Research Center-Gorgan, Iranian Fisheries Sciences Research Institute, Agricultural Research Education and Extension Organization (AREEO), Gorgan, Iran Seyyed Morteza Hoseini1 سید مرتضی حسینی1 seyyedmorteza.hoseini@gmail.com 100319475328460012308 100319475328460012308 No Melika Ghelichpour1 ملیکا قلیچ پور1 ml.ghelichpour@gmail.com 100319475328460012309 100319475328460012309 No sara Haghparast سارا حق پرست sarah_haghparast@yahoo.com 100319475328460012310 100319475328460012310 No گروه شیلات، دانشکده علوم دامی و شیلات، دانشگاه علوم کشاورزی و منابع طبیعی ساری، ساری، ایران Abdollah Haghpanah1 عبدالله حق پناه1 haghpanah_a@yahoo.com 100319475328460012311 100319475328460012311 No Behruz Garavy1 بهروز قره وی1 behroozgharavy@yahoo.com 100319475328460012312 100319475328460012312 No