The management design of Lake Kinneret encountered presently a decision- making d
During the last 20 years, the Kinneret ecosystem structure has undergone significant modifications. The algal dominance of the bloom forming Peridinium was replaced by Cyanobacteria, and the fish pelagic food resources were modi- fied by intensification of zooplankton suppression. The landings of S. gal
The optimization of the fishery management crucially includes a comprehensive involvement of a wide range of ecosystem’s structural parameters where fishermen’s income, nature conservation, and water quality protection, including water level fluctuations (WLF), are integrated. The objective of this paper is an insight into a solid scientific information and into what is presently accounted as the virtual concept of “Prevention by Carefulness” (have been defined by UNESCO in 2005 as: “The Precautionary Principle”) as crucial service for decision making regarding the littoral management program aimed at both human welfare, lake water quality and nature preservation.
The food components of fish larvae when compared to their counterpart, adult stages, are essentially different within the food-web structure    . Planktivory is a dominant feeding trait among the Kinneret fishes wh
2. Material and Methods
Water Level Fluctuations (WLF) (Figure 1).
In order to find a potential relation between WLF, cover intensity of beach vegetation, bottom substrate feature and fingerling food composition, the data on WLF was evaluated. The merit of aquatic plant bottom cover to fingerling survival was also considered because of substrate ava
The littoral zone is determined in this paper as the shallow water zone limited between depth bordered between 0 to 1.5 meters. In multiannual considerations this shallow belt is changed according to WLF. The index of Water Level Fluctuation was calculated by averaging monthly changes of the water level i.e. Periodical (annual groups) Sum of (WL0 − WLt) monthly values in m divided by 100 to get it in cm units throughout the total year group period.
Figure 1. Fractional Polynomial of monthly means of Water Level in Lake Kinneret during 1936-2016. Row of numbers are Decade (Table 1) averaged WL (upper) WLFI (lower) (see text).
WL0 = Monthly mean of initial WL.
WLt = Monthly mean WL one month later than WL0.
WLFI = The total summary of (WL0 − WLt).
Example: If (WL0 − WLt) = 0.3 (increased WL) and the consecutive value is −0.3 (WL decline) the index is 0.
2.1. Beach Vegetation Mapping 
A set of Air Photos of the Kinneret Beach vegetation in the vicinity to the entire shoreline was carried out in 5.5.2012 when WL was high (Figure 1) by A. Dori, National Authority of Nature Conservation and National Parks, and decoded and published by Kinneret Limnological Laboratory. Total number of photos were 600, more than 10 per 1 km of beach. Three levels of vegetation density were indicated: 1) Dense-45% of shoreline total length; 2) Dispersed-16% of total shoreline length; 3) No vegetation-39% of total shoreline length. The level of vegetation cover was encoded by topographic visualization of combined air photos indicating density level as dullness performance in the photos.
2.2. Statistical Methods
Statistical analyses used in this study were taken from STATA 9.1, Statistics-Data Analysis and StatView 5.1, SAS Institute Inc. The analyses used were: ANOVA (p < 0.05), Polynomial and Linear Regressions, Fractorial Polynomial Prediction, LOWESS (0.8).
2.3. Water Level Record
Monthly averages of the Kinneret Water level was taken from the Lake Kinneret Data Base-Tahal and Water Authority (1936-2016). The long monitored period of 80 years, started after the construction of the south Dam (1936), until 2016, was grouped into 8 periods of 10 years each (Table 1).
Figure 1 represents annual means of WL in Lake Kinneret during 1970-2015 and two levels are lined: 1) 212 MBSL indicating common altitude prior to the operation of the National Water Carrier (1964); and 2) 213 MBSL which is the present legislated lowest permitted WL altitude whilst actually lower than that was quite often managed.
Table 1. Periodical decades used in this paper.
2.4. Fingerling Sampling
Fingerlings were sampled monthly by Electro-Shocker at 0.0 - 1.0 m depths at 10 stations along the entire lake shoreline. The bottom substrates in the sampling sites were varieties of muddy-sandy-pebble and stony compositions. Fingerlings were captured, identified, counted and body length was monitored. Five specimens of each sampled species were sub-sampled, preserved immediately in 10% formalin solution and later dissected for the analysis of the gut contents under dissecting and inverted light microscopes.
2.5. Fingerling Food Composition
Earlier studies about the feeding habits of Bleak (Acanthobrama terraesanctae terraesanctae and Mirogrex lissneri) fingerlings    indicated free swim- ming zooplankter as the major food component. The fingerlings of the following species are presented in this study: Astatotilapia flavijosephi, Salaria fluviatilis, Barbus canis, Clarias gariepinus, Garra rufa, Hemigrammocapoeta nana, Tristramella simonis simonis, and Neomachilus leantinae.
2.6. Commercial Fisheries
Data on Commercial Fisheries in Lake Kinneret is routinely published (Fisheries Department 1950-2017) and results given in special report (2000-2015)  were accounted here. The data selected for the present study refer to the two relevant native nest-builder-mouth-breeder tilapia species: Tristramella simonis simonis and Sarotherodon galilaeus and the most abundant species, the endemic Bleaks (Acanthobrama terraesanctae terraesanctae and Mirogrex lissneri)  .
3.1. Water Level Fluctuation Index (WLFI)
Results given in Figure 1 (average WL per decade) indicate Water Level (WL) elevation from the 1st (−210.6 MBSL) to the 4th decade (−209.8 MBSL), and from the 5th through the 8th decade a decline of WL by 2.6m.
The monthly changes of WL were calculated by subtraction of each monthly mean WL from previous monthly mean value. During the winter months it was obviously mostly positive value (i.e. an increase) wh
Table 2. Water Level Fluctuation Index (WLFI) (cm) per Decade (see Table 1).
Results in Table 2 emphasize three periods of high WLFI values caused by exceptional WL fluctuations: During the 1946-1955 high amplitudes of increasing WL management, the higher WLFI values were caused by a succession of droughts and heavy floods events (Figure 1).
3.2. Gut Content Composition
The numerical composition of gut contents as averaged for 5 specimen of each species per sampling station is given in Tables 3-10. The body size of the fingerlings is given. Composition was classified in three levels of frequency: 1) Abundant (above 50% of observed items); 2) Medium (between 10% - 50% of observed items); 3) rare (less than 10% of observed items). Sampling stations (numbered with local name) were as follows.
A: Western side of the lake: No.1:Biriniki; No.2: Migdal; No.3: Ginosar; No. 4: Ohalo; No.5: Lido. No.6: Ginosar-Arbel;
B: Northern part: No.7: Amnon Bay;
C: Southern part: No.8: Maagan;
C: Eastern part: No.9 Ein-Gev ; No.10 Ein-Gev South.
The food composition of fingerlings of Coptodon (Tilapia) zillii was given in  .
Results in Table 3 indicate food collections by a bottom shallow dwelling. The fingerlings of A. flavijosephi are not a f
Results given in Table 4 indicate the feeding habits of Barbus canis as stone scraping or delving into sandy substrate.
Results given in Table 5 indicate that Clarias gariepinus is an omnivore feeder fish (Spataru et al., 1992) which feeds on items that are most ava
Garra rufa preferably populates the Kinneret littoral environment where food is collected from sandy or muddy bottom resources. Due to the high density of G. rufa within the littoral ecosystem, its organic matter recycling capab
Table 3. Species: Astatot
Table 4. Species: Barbus canis; Body size (TL cm): 8.0 - 10.0. Sampling Time: June-Au- gust.
Table 5. Species: Clarias gariepinus; Body size (TL cm): 23.0 - 70.0. Sampling Time: January-June-August.
Table 6. Species: Garra rufa; Body size (TL cm): 6.0 - 4.0. Sampling Time: June-Septem- ber.
Table 7. Species: Hemigrammocapoeta nana; Body size (TL cm): 8.0 - 4.0. Sampling Time: August.
Table 8. Species: Salaria fluviat
Table 9. Species: Tristramella simonis simonis; Body size (TL cm): 8.0 - 3.0. Sampling Time: June-August.
Table 10. Species: Neomach
Results given in Table 7 indicate the feeding habits of Hemigrammocapoeta nana as stone scraping or delving into sandy substrate.
The population of the Cichlid T. simonis simonis is presently in serious decline, but our sampling confirmed the existence of a high concentration of YOY fingerlings. Feeding trait is considered as bottom dwelling.
Food item collection by N. leantinae is indicated as stone scraping wh
3.3. Food Composition―Location and Beach Vegetation
The potential linkage between gut content composition and vegetation cover or bottom type affinity was suspected. Therefore, gut content compositions of all individuals and all species sampled in a site were pooled together for site comparison (Table 10) and combined with plant cover level information  .
3.4. Commercial Harvest of Kinneret Native T
Fishing motivation and, consequently, effort investment depend solely on market demands. Therefore, precaution should be accounted for the evaluation of relating stock assessment to commercial landings. During 2007-2011, a significant decline of S. galilaeus harvest was documented and similar decline timing was indicated for T. simonis and Bleaks. Among those three species, much higher fishing motivation is given to S. gal
The history of human intervention (anthropogenic management) in the management of the Lake Kinneret ecosystem started in 1933 when the South Dam (Deganiya Dam) was constructed. Earlier (1918), a wooden bridge located at the outlet site of the river outlet was constructed. The 1918 bridging between the two river banks did not modify the Lake’s natural conditions of water budget or rate of exchange. The south dam construction granted partial control of water ba-
Table 11. Air Photo documented Beach Vegetation cover is classified into three levels: 1) Dense cover (45% of the entire beach belt); 2) Dispersed cover (15% of the entire beach belt); 3) Un-covered (39% of the entire beach belt)  . Food components that were documented in all 5 fingerlings that were sampled in those sites (1 - 10) (See Material and Methods).
Table 12. Decades (See Table 1) mean (± SD) landing harvests of Bleaks, S. galilaeus and Tristramella simonis simonis (tons). SD = 0 insufficient data record.
lance and consequently Water Residence Time (WRT) and Water Level Altitude (WLA) and several other consequences. Nevertheless, lake ut
Results presented in Tables 3-11 indicate the bottom feeding trait of fingerlings in the Kinneret Littoral habitat. Unlike f
Vegetation, WLF, and Fingerling Abundance
Until late the 1990’s WL fluctuated mostly around 212 MBSL. The result was continuity of water cover of the half-open lagoons in the Beteicha valley connected to the north-east shoreline of lake Kinneret. This lagoon area was highly populated by Tilapia spawners    . Surveys carried out in the littoral zone of Lake Kinneret during the late 1980’s  indicated high densities of fingerlings in the shallows with not significantly linked to vegetation. About 100 - 131 Fingerlings (1 - 10 cm TL) of C. zillii were captured by Electro-Shocker in a shallow water area, not plant covered, of 5 - 10 m2 within 10 - 15 minutes  . Long-term decline of WL below 212.50 caused a complete elimination of T
It is suggested that WL fluctuations (high values of WLFI) affected the production of T
Table 13. Annual (2000-2015) landings (ton) of Sarotherodon gal
Table 14. Decade Averages of the Kinneret monthly Water Level (MBSL) means.
Tilapias production. Moreover, the partial elimination of inundated beach vegetation factor as production improvement for T
The causation of environmental constraints on the Kinneret littoral ecosystem processes was analyzed. Among environmental factors, Water Level Fluctuations, inundated beach vegetation and food resources for fingerlings were considered. The potential influence of water Level and spawning ground ava
I wish to express my thanks to Dr. O. Sonin, Z. Snovski and J. Shapiro, from the Fishery Department, Kinneret Fishery, Ministry of Agriculture and Villages Development, for supporting of facilities and field assistance in fingerlings sampling in the littoral; Project No. 596-0527-12 to M.G.
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 El-Bolock, A.R. and Koura, R. (1961) The Age and Growth of Tilapia galilaea Art., T. nilotica L. and T. zillii Gerv., from Beteha Area (Syrian Region), Notes and Memoires No. 59, United Arab Republic (Southern Region), Ministry of Agriculture; Hydrobiological Department, Institute of Freshwater Biology, Gizira-Cairo, 1-27.
 Shefler, D. (1987) Some Observations on the Fish Nurseries along the Lake Kinneret Shores: The Interrelationships between Species and the Influence of Environmental Factors. Journal of Applied Ichthyology, 3, 105-114. (In Hebrew, English Abstract)