MAJOR: ASPECTS OF ECOLOGY OF STRIPED MULLET 



Table 1. — Summary of experimental conditions and fish statistics. 



Experimental 



salinity (%«) 



(actual test 



salinity) 



34(32) 

 32 

 34 



34(33) 

 33 



34(36) 

 34 

 32 

 32 



15(16) 

 (14) 

 (15) 



15(14) 

 15 



Month and 



year of 

 experiments 



Min-max 



tank temp 



CC) 



Length to 



nearest mm 



17-19 20-29 30-39 40-49 50-59 60-69 70-79 80-130 Mean (range) 



Number fish in size range (mm SL) 



Total Experimental 

 number group code 

 fish (see Figure 3) 



Feb 1972 

 Mar 1972 

 Mar, 1972 



May 1972 

 May 1972 



July 1972 

 July 1972 

 Mar 1973 

 Mar 1973 



Jan, 1972 

 Mar 1973 

 Mar, 1973 



Aug, 1972 

 Mar. 1973 



Feb 1972 

 Mar 1972 

 Mar. 1972 

 Mar 1973 



May 1972 



Jan. 1973 

 Mar. 1973 



16.8-360 

 15.1-38.6 

 170-40.1 



17.8-40.8 



17.5-41.0 



15.8-39.2 

 15 0-39.2 

 150-378 

 17.0-40.0 



169-40.0 

 13.0-39 

 132-39.9 



15.5-39.8 

 14.1-39.8 



15.9-36.9 

 164-389 

 160-40.1 

 148-39.0 



17.0-38.5 



18.8-38.2 

 162-386 



36 



39 

 3 



78 



13 

 39 

 27 



79 



26 

 36 

 47 

 35 



144 



11 

 29 



40 



7 



3 

 23 



26 



10 

 2 



16 

 10 



2 



29 



14 



43 



19 



2 



17 



19 



5 



7 



12 



12 



24 

 27 



34 



(19-28) 

 (21-38) 

 (29-43) 



28 



42 

 51 



(19-43) 



(37-52) 

 (46-59) 



7 



10 



9 



2 

 11 

 22 

 20 



46 



68 



75 



80 



109 



(37-59) 



(55-83) 

 (56-98) 

 (48-103) 

 (82-129) 



26 



55 



82 



27 

 26 

 28 



(48-129) 



(24-31) 

 (19-29) 

 (20-39) 



18 

 10 



26 



88 

 98 



(19-39) 



(69-114) 

 (75-125) 



28 



26 

 22 

 27 

 26 



(22-34) 

 (19-26) 

 (17-34) 

 (21-31) 



35 

 16 



24 



43 



98 

 102 



(17-34) 



(35-51) 



(76-118) 

 (87-130) 



122 ; 



69 



106 



106 J 



92 (69-125) 33, 



51 



99 (76-130) 52 



A1, 2, 3 



B1, 2, 3 



CI, 2, 3 



D1, 2, 3 



El, 2. 3 



F1. 2, 3 



G1, 2. 3 



HI, 2, 3 



nected to reservoirs circulated v/ater, chilled as it 

 passed through a set of coils in an ice bath, before 

 entering the bottom of the tank, and water heated 

 by a braided glass heating tape wrapped around a 

 section of the coil, before it passed into the tank at 

 the surface. The reservoirs allowed air bubbles to 

 escape and the addition of water to the coils. 



Vinyl-coated thermistor probes (and leads), ex- 

 tending through plastic tubes to various levels in 

 the tank, ran above the top of the tank and out to a 

 telethermometer recorder. 



Fine mesh plastic window screen was attached 

 to the inside circumference of the coils to keep fish 

 in the central area of the tank. The volume of 

 water in the tank available to the fish was approx- 

 imately 486 1, 88 cm in diameter and 80 cm deep. 

 Observations were made through narrow eye- 

 width slits cut at various levels in each side of the 

 enclosure. A light-excluding cover surrounded the 

 observer during observations. The viewing slits 

 were closed when not in use. 



Water samples were taken from the surface, 

 middepth, and bottom before and after each exper- 

 iment for oxygen, pH, and salinity analysis. Oxy- 

 gen measurements could not be made con- 



tinuously during the experiments, but oxygen 

 measurements before and after each experiment 

 did not change noticeably. In addition, respiratory 

 movements of mouth and opercles, which might 

 have been indicative of oxygen deficiencies, in the 

 mullet did not change with increased heating. The 

 above measurements were made primarily to en- 

 sure that mullet were not orienting to factors 

 other than temperature. 



Illumination was provided by two 15-W incan- 

 descent light bulbs fixed in reflectors 84 cm above 

 the surface of the water. Due to the position and 

 low wattage of the light sources, a light gradient 

 was established in the tank. The behavioral and 

 distributional responses of the fish in a continu- 

 ously changing thermal environment indicated 

 that orientation to temperature and not light gra- 

 dients occurred. The same observations were used 

 to control for any orientation to pressure gra- 

 dients, which inevitably existed in the 80-cm deep 

 tank. 



One of three experimental salinity conditions, 

 freshwater (range 0-2%o), 15%o (range 14-16%o), 

 and 34%o (range 30-36%o), was established prior to 

 placing the fish in the tank. Freshwater was 



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