Monday, November 2, 2015

Inland Fisheries Research, October 2015 monthly progress


Compiled by: Mr. Francois Jacobs              
Senior Fisheries Biologist (KIFI)


Progress for study titled: Evaluating the tag retention potential and effects of plastic tipped dart tags, PIT tags, internal and external radio transmitter on the health of social economic important freshwater fish species.

Tagging of fish species in the display aquarium was initiated on the 30th of September and forms part of the study titled: Evaluating the tag retention potential and effects of plastic tipped dart tags, PIT tags, internal and external radio transmitter on the health of social economic important freshwater fish species. In brief:
Fishes were conditioned in aquarium facilities and general environmental conditions were kept constant. Individual fishes were collected using a hand held scoop net. Suitable fishes were submerged in an aerated tagging container, after which 10ml clove oil (0.5 ml.l−1) was added until signs of narcosis became evident. Tagging equipment was cleaned in ethanol before use and hands were sterilised with Betadine (Adcock Ingram Ltd, Bryanston, South Africa). Thereafter PIT tags (10.3 mm x 2.1mm in diameter) with a coil and integrated circuit, were inserted into the peritoneal cavity or musculature of fishes using a syringe injector. Thereafter fish were allowed to recover and released back into aquarium.
A total of 30 C. rendalli were tagged in the display aquarium. These fish ranged in size (80 min – 185 max) with an average total length of 126.1 mm (Table 1). An additional 10 C. rendalli was included in this experiment as a control. Apart from minor injuries obtained during the tagging procedure the fish in general show full recovery. After two weeks of observation, their feeding continues normal with no unnatural/erratic behavioural alterations caused by insertion of tags. This species has thus far maintained a 100% tag retention rate and a 97% survival rate. Continues monitoring is being carried out.

Table 1: Coptodon rendalli that was PIT tagged in the Aquarium of KIFI to assess: tag retention potential and general fish health of this species. 
(click on image for a better view)


          
Progress for study titled: The life history strategies of two social economic important freshwater fish species Serranochromis angusticeps and Serranochromis altus in the Kavango River.
This study aims to identify the life history strategies of two sympatric large predatory fish species (Serranochromis altus and Serranochromis angusticeps) which has commercial, subsistence and recreational importance in the Kavango River. This aims to provide biological and ecological research outputs that can help facilitate communities in the management of the resources upon which they largely depend for food security and income generation.
There are numerous methods that can be used to capture fishes during surveys. Each method needs careful consideration to prevent unrepresentative sampling and biased statistics (Rogers and White, 2007). This study identified two types of angling disciplines best suited for these species including:
ü  Fly-fishing techniques where anglers use artificial flies made from synthetic material to represent natural food.
ü  Artificial lure fishing involves using lures made from balsa wood, iron or hard plastic (Rapalas®, Blue Fox spinners®, Action Lures®) to represent live swimming baitfish.  
After capture suitable fishes were submerged in an aerated tagging container, after which 10ml clove oil (0.5 ml.l−1) was added until signs of narcosis became evident. Tagging equipment was cleaned in ethanol. Thereafter PIT tags (10.3 mm x 2.1mm in diameter) with a coil and integrated circuit, were inserted into the peritoneal cavity or musculature of fishes using a syringe injector (Figure 1). Thereafter fish were allowed to recover and released back into natural environment.

This study has PIT tagged 49 individual S. altus ranging in sizes from 300 mm to 490 mm total length. These fish were all captured with angling and stress to fish was minimized by limiting holding time to a few seconds (average +-20 sec). Habitats where individuals were captured included (SD <0.3m s 1>0.5m) deep pools and backwaters, (FD >0.3m s-1>0.3m) deep, runs, rapids and riffles.  The dominant substrate within these habitats were sand (60%), clay/mud (10%) and boulders (30%) with cover features column (40%) and overhanging vegetation (60%) being the most important (Figure 2). These habitats are typical for this species which ambushes mostly mormyrids and silver catfish from these vantage points.
(click on image for a better view)
Figure 1: Tagging station was set up in advance (A), after which 10ml clove oil (0.5 ml.l−1) was added until signs of narcosis became evident. Tagging equipment was      cleaned in ethanol before use, thereafter PIT tags (10.3 mm x 2.1mm in diameter) with a coil and integrated circuit, were inserted into the peritoneal cavity of fishes using a syringe injector (B-D) and unique code was read and recorded (E), measurements taken and a quick profile picture taken before release (F). (Note an unexpected Nembwe was captured during collection and also received a PIT tag photo D and E) 

(click on image for a better view)


Figure 2: Typical habitat of Serranochromis altus in the Kavango River


Table 2: Serranochromis altus, PIT tagged in the Kavango River for the long term behavioural monitoring programme, including number, date, time, tag number and measurements 
(click on image for a better view)

Aquarium and staff initiative

The tanks in the aquarium was upgraded for display purposes. The staff test which is an initiative to get people involved and interested in various fish species was written on the 16 October 2015 at 2 o’clock in the KIFI boardroom (Figure 3). Mr Christian Muyambo received an 80% test score and was the winner of the staff award for his performance.

Figure 3: Staff test being written in the KIFI boardroom
Upgrading the aquarium also resulted in creating the right breeding conditions for a male and female C. rendalli which produced a hatch of fry. These fish were captured during brood stock collection on the 18th September 2015 and could be witnessed constructing a nest two weeks before breeding took place. As the nest developed a distinct colour change took place in both sexes. Three days before the fry could be seen the male and female displayed erratic movements and their colours were noticbly bright. The eggs hatched on the morning of the 08th October 2015 at 26 °C after which continues hatching took place until the evening (Figure 4).  The fry is being measured weekly for growth estimates.
(click on image for a better view)
Figure 4: Coptodon rendalli eggs gently positioned between substrate (A-B), the first hatchlings (C) and both male and female guarding their new born fry in a display tank at KIFI. Fry were born on the morning of the 8 October 2015. 
Figure 5: KIFI staff members receiving training on maintaining and calibrating water quality meters in KIFI boardroom.

No comments: