Distribution of Five Macrobrachium Species Along a Salinity Gradient in Rivers State, Nigeria

London Journal of Research in Science: Natural and Formal
Volume | Issue | Compilation
Authored by Adaba Ibim , NA
Classification: FOR Code: 279999
Keywords: abundance, bonny and new calabar rivers, distribution/salinity Range, macrobrachium species, salinity gradient.
Language: English

A study was carried out to determine the distribution of five Macrobrachium species (M.dux, M.vollenhovenii, M.macrobrachion, M.felicinum and M.equidens) along a Salinity gradient in the New Calabar and the Bonny Rivers, in Rivers state. The aim was to identify the preferred salinity range and tolerance of these species in the field. Subsequently, a five-month field survey was conducted in six sample stations along the Bonny and New Calabar Rivers. Once weekly, the Salinity regime of the sample stations was determined by ascertaining the Salinities of the water samples from the stations using a Salinometer, and by the criteria of Rogers et al. (2003). Simultaneously, Prawn samples were collected from the stations using indiscriminate nets and traps, identified; and their distribution(range) and abundance in the stations assessed, using standard methods. Results revealed the Salinity gradient in the stations along the Bonny and New Calabar Rivers, with Isiokpo as Freshwater (0 ppt); Aluu and Choba Oligohaline (0ppt to 1ppt, and 1ppt to 4ppt; respectively); Rumuokparali (10ppt and 14ppt) and Ogbogoro (14ppt and 16ppt) being Mesohaline. Bakana (16ppt and 18ppt) fluctuates between meso- and polyhaline, while the Isaka area is Polyhaline (20ppt and 25ppt). The identification of the different species of the Macrobrachium, their distribution and abundance in the Salinity gradient showed that the M.equidens are Polyhaline, existing between 15ppt to 24ppt. M. macrobrachion (in 0ppt to 15ppt) and M. vollenhovenii (in 0ppt to 16ppt) are euryhaline species, cutting across a wide Meso to Oligohaline environment. M. felicinum found in 0ppt to 1ppt waters, and M. dux in 0ppt waters only, are Oligohaline and Freshwater species, respectively. It was observed that all these species especially, M. equidens, have distribution patterns which vary from their distribution in other rivers globally. Secondly, the M. vollenhovenii and M. macrobrachion species occupy thesame salinity gradient but are prominent at different times of the day, with M. macrobrachion more active in the day and the M. vollenhovenii at night time. In conclusion, the Bonny and New Calabar Rivers stretch showcases a Salinity gradient ranging from brackish to fresh waters. The different Macrobrachium species are prevalent in this Salinity gradient. However, their abundance and distribution vary widely along this gradient. The reason for this variation is not known, but it is suspected to be as a result of several biotic or abiotic factors that interplay and not salinity alone. It is therefore recommended that studies of several abiotic and biotic factors be carried out simultaneous, to ascertain the true reason for the variation along this Salinity gradient and other habitats where they occur. This will go a long way in understanding their biology, culture and the management of the fishery of these economically important species.

               

Distribution of Five Macrobrachium Species Along a Salinity Gradient in Rivers State, Nigeria

Ibim, A.T.

____________________________________________

  1. ABSTRACT

A field survey was carried out to determine the distribution of five Macrobrachium species (M. dux, M. vollenhovenii, M. macrobrachion, M. felicinum and M. equidens) along a Salinity gradient in the New Calabar and the Bonny Rivers, in Rivers state. The aim was to identify the distribution, preferred salinity range and tolerance of these species in the field. Subsequently, a five-month field survey was conducted in six sample stations along the Bonny and New Calabar Rivers.  Once weekly, the Salinity regime of the sample stations was determined by ascertaining the Salinities of the water samples from the stations using a Salinometer, and by the criteria of Rogers et al. (2003). Simultaneously, Prawn samples were collected from the stations using indiscriminate nets and traps, identified; and their distribution (range) and abundance in the stations assessed, using standard methods. Results revealed the Salinity gradient in the stations along the Bonny and New Calabar Rivers, with Isiokpo as Freshwater (0 ppt); Aluu and Choba Oligohaline (0ppt to 1ppt, and 1ppt to 4ppt; respectively); Rumuokparali (10ppt to  14ppt) and Ogbogoro (14ppt  to 16ppt) being Mesohaline. Bakana (16ppt to  18ppt) fluctuates between Mesohaline and Polyhaline, while the Isaka area is Polyhaline (20ppt to  25ppt). The identification of the different species of the Macrobrachium, their distribution, and abundance in the Salinity gradient showed that the M. equidens are Polyhaline, existing between 15ppt to 24ppt. M. macrobrachion (in 0ppt to 15ppt) and M. vollenhovenii (in 0ppt to 16ppt) are Euryhaline species, cutting across a wide Mesohaline to Oligohaline environment. M. felicinum found in 0ppt to 1ppt waters, and M. dux in 0ppt waters only, are Oligohaline and Freshwater species, respectively. It was observed that all these species especially, M. equidens, have salinity ranges/distribution patterns which vary from their salinity ranges/distribution in other rivers globally.  Secondly, the M. vollenhovenii and M. macrobrachion species occupy the same salinity ranges/distribution but are prominent at different times of the day, with M. macrobrachion more active in the day and the M. vollenhovenii at night time. In conclusion, the Bonny and New Calabar Rivers stretch showcases a Salinity gradient ranging from brackish to fresh waters. The different Macrobrachium species are prevalent in this Salinity gradient. However, their abundance and distribution vary widely along this gradient. The reason for this variation is yet to be known, but it is suspected to be as a result of several biotic and abiotic factors that interplay and not salinity alone. It is therefore recommended that studies of several abiotic and biotic factors be carried out simultaneous, to ascertain the true reason for the variation along this Salinity gradient and other habitats where they occur. This study will go a long way in understanding the biology, culture and the management of the fishery of these economically important species.

Keywords:   abundance, bonny and new calabar rivers, distribution/salinity range, macro- brachium species, salinity gradient.

Author: Department of Fisheries, Faculty of Agriculture University of Port Harcourt, Rivers State, Nigeria.

  1. INTRODUCTION

The Prawns of the genus Macrobrachium and Peneaus are of high economic importance world-wide and are highly cherished by the coastal dwellers in Rivers State, Nigeria. Prawns are an important source of animal protein especially for the rural coastal dwellers (Eniade and Bello-Olusoji, 2011). They are used as food fishes, and condiments in the preparation of food because of their delicious flavor and high protein value (Deekae and Idoniboye-Obu, 1995). Nigeria is among the tropical countries endowed with rich shrimp resources, and as a direct result of the soaring demand for shrimp in international markets and the attractive foreign exchange it earns the demand for these species have increased.

The most common prawn species found in Nigerian rivers are the Macrobrachium species (Eniade and Bello-Olusoji, 2011). They reported that the Macrobrachium species are fresh and brackish water prawn species, whose larval development takes place in high salinity waters. There are four known species of the Macrobrachium indigenous to Nigeria, and one exotic introduced species namely, M. dux, M. vollenhovenii, M. macrobrachion, M. felicinum and M. equidens (Powell, 1980; Lawal-Are and Owolabi 2012). The Macrobrachium species occur commonly in the West African region and their distribution, local names, habitat, and sizes have been reported by Powell (1983). The total lengths of these shrimps in the wild are reported to range from 80 mm in the smallest species Macrobrachium felicinum, to 190 mm in the larger species Macrobrachium vollenhovenii (Opeh and Udo, 2014 ).

Lawal-Are and Owolabi (2012) reported that most of the species of Macrobrachium are large prawns that are commercially cultured, and have been subjected to intense aquacultural practices in developed countries especially in Asia and the Americas, where Macrobrachium rosenbergii is one of the best-farmed species in this family. FAO (2006) in Deekae and Abowei (2010) reported that global production of M. rosenbergii increased to over 200,000 tonnes/yr by 2002. In Nigeria, fisheries interest in shrimps has been centered on the marine Penaeid species mainly Penaeus notialis, harvested offshore by commercial trawlers (Powell, 1985).  However, these species are known to support the traditional artisanal fisheries and are in high demand in the market (Marioghae, 1990). They are considered suitable candidates for aquaculture (Powell, 1983; Marioghae, 1990; Lawal-Are and Owolabi, 2012).

Several studies have been carried out on various aspects of the Macrobrachium species and on their distribution in different parts of the country where they occur. These include; Salinity tolerance of the M. vollenhovenii in Asejire Lake, Oyo State, Nigeria (Anetekhai, 1989); Sexual dimorphism of the M. vollenhovenii in Asejire Lake, Oyo State, Nigeria (Anetekhai.1990). Also included are, the Reproductive biology and culture of the Macrobrachium vollenhovenii (Herklots 1857) and Macrobrachium macrobrachion (Herklots 1851) in Lagos Lagoon, Nigeria (Marioghae and Ayinla, 1995); The recruitment pattern in the Lagos-Lekki Lagoon system (Bello-Olusoji et al.,1995); the Effect of the food of the larvae on the food and feeding habits in Epe Lagoon (Jimoh et al., 2009); Macrobrachium macrobrachion (Herklots, 1851); Class Structure and Sex Ratio in Luubara Creek, Ogoni Land, Niger Delta, Nigeria, (Deekae and Abowei, 2010);  and Fecundity of Brackish River Prawn (Macrobrachium macrobrachion, Herklots, 1851) from Great Kwa River, Obufa Esuk Beach, Calabar, Cross River State, Nigeria (George et al., 2013). Powell (1985 and 1987) worked on several areas and several issues of these Macrobrachium species in the Niger Delta Area and generated a generalized document for their biology and occurrence. However, there is no information on the distribution of the species along a salinity gradient in the Bonny and New Calabar Rivers, in Rivers State.  Thus, this research is targeted at delineating the preferred habitat of the five species of Macrobrachium in the Bonny and New Calabar Rivers, in Rivers State. This scientific information is vital in enhancing the development of the Culture technique of these Macrobrachium species.

  1. MATERIALS AND METHODS

3.1  Study Area Description

F:\_\New folder\New folder\new calabar.png

Figure 1: Map of the Study Area: Rivers State, Nigeria, showing sampling Stations A(Isiokpo), B(Aluu), C(Choba), D(Rumuokparali, Uzoba), E(Ogbogoro), F (Bakana) in the New Calabar River and G (Isaka) in the Bonny River.

As shown in Figure 1, the study was carried out in two (2) Rivers namely, the New Calabar and Bonny Rivers, located in the Rivers State, Nigeria.

The New Calabar River is located on Latitude: 4°25¹ ON; Longitude: 7°16¹ OE, in the Niger Delta, a central part of Southern Nigeria (NDES, 2003). It has tributaries which lie between the coordinates; 4o 29’54”N 6o 59’46”E / 4.498393o N 6.996231o E / 4.498393; 6.996231. The river is located on the eastern flank of the Niger Delta River System, in Rivers State. Deinye and Woke, 2015 reported that the New Calabar river is mainly tidal with a moderate water current. The tidal nature of the river is indicative of well mixed, unsteady floodtide and ebbtide flows. However, it rose from Elele-Alimini where it is fresh and non-tidal (Erondu and Chindah, 1991), from where it flows downward to Aluu, where it is still fresh but tidal (Deinye and Woke, 2015).   At Aluu, it is joined by a smaller tributary river which took its rise at Isiokpo (Deinye and Woke, 2015). Further downstream, at the Choba to Ogbogoro axis, it becomes brackish. This brackish nature continues downward to Bakana, from where it connects Isaka in the Bonny River via a creek.

The vegetation is thick rain, swamp forest with gently sloping topography (Deinye and Woke, 2015). The plants encountered in the lower brackish areas are mainly the Red mangrove, whereas the fresh water areas have various terrestrial flora especially, aquatic macrophytes. The New Calabar river basin experiences an annual rainfall of 254 mm (Erondu and Chindah, 1991). This River is a black water type (RPI, 1985). The substrate encountered in the lower brackish water areas consist of chikoko mud and some sand whereas the upper fresh water areas (the Aluu and Isiokpo areas) have sandy banks and sea beds, with a lot of logs of wood around the shores and within the water bodies.

The New Calabar River is also connected to the Bonny River which is another river in the Niger Delta river system (Dublin-Green, 1990). The Upper Bonny River is where the Isaka sampling station is located. This section of the Bonny river system is characterized by the interaction of estuarine and highly saline seawater located seaward of the river mouth (typical of the Niger Delta coastal region), and influenced by tide and wind-driven surface currents (Babatunde et al., 2013). The Upper Bonny River lies Southwest of Port Harcourt. Ngah et al.(2017), reported between longitude 04˚46'743"N and 007˚00'557" E; 04˚48'217"N, and 006˚48'989"E and that it is protected from strong wave actions prevalent in the main Bonny River Channel and the current flow velocity is minimal (about 3 m/s). They further stated that the area enjoys tropical equatorial climate with the surface seawater temperature varying between 25.9˚C and 30.6˚C. The sediment which is dark in color consists mainly of chikoko, moderate sand to silty clay. In Isaka the substrate encountered is high and steep banks of chikoko mud and some sand. Flood plains border the River and its creeks of which Isaka is one, and these are well exposed at low tides (Abowei, 2009). The vegetation is characteristically mangrove, with the dominant red mangrove (Rhizophora racemosa), white mangrove (Avicennia africana) and black mangrove (Laguncularia racemosa) and other plants (e.g., fern-Achrostichum aureum and grass-Paspalum varginatum), (Ngah et al., 2017). The Climate over both Rivers is tropical, having two major seasons; the dry season during November to March, and rainy season, April to October.

Both economically important in Rivers State as they are in the vicinity of the rapidly expanding oil city of Port Harcourt in Rivers State, Southern Nigeria, serving as major transport and communication media, serve as important water, fish food and protein sources, and most importantly Hydrocarbon (Energy) sources for economic development of the country Nigeria.

3.2  Sample stations

Six (6) sample stations were randomly picked along both rivers spanning from Upper section of the New Calabar River (Isiokpo) inwards to the Bonny River (Isaka). The sample stations picked were; Station A - Isiokpo), B- Aluu, C - Choba, D -  Rumuokparali, Uzoba, E - Ogbogoro, F - (Bakana, all in the New Calabar River; and Station G – Isaka, in the Bonny River; as shown in figure 1.

3.3  Field Studies

3.3.1 Prawn Sample Collection

Field surveys were carried out for five months from November to March in the various sampling stations.  Fishing was carried out at low tide, to ensure easy collection of prawns. A variety of fishing gears were employed for catching the prawns among which were, Non-return valve traps of approximate dimension of 65 x 40 x 25 cm, with opening of about 20cm in diameter, used at river banks. Also used were drag nets of about 2m in length with spread circumference of about 10m made from 75mm size mesh, used for Prawn collection from a considerable depth in the river.  Hand nets were also used to scoop the muddy substrate and collect water around aquatic vegetation. The fishing was done in the morning between 10 a.m. and 12 p.m., and in the evenings between 6.00pm and 8.00p.m. The fishing process was repeated severally, at every fishing time to ensure abundant catch and prawn species collection.

3.4 Data Collection

3.4.1 Sample Stations Salinity Determination

The salinity of the sample stations was assessed by collection of water in sample bottles from the sampling stations, once weekly, for the 5 months of the study. These water samples were taken to the Laboratory to determine the salinity of the samples for the stations. The water was collected at ebb tide and when it was reversing. The Salinity of the water samples were measured using a Salinometer and, recorded in parts per thousand (ppt). Furthermore, the criteria of Rogers et al., (2003) was applied to classify the river salinity into five categories thus;   Fresh (<0,5ppt); Oligohaline (0.5 – <5ppt); Mesohaline                 (5- <18ppt); Polyhaline (18 - <30ppt)  and Euhaline (30 - <40ppt).

3.4.2 Prawn Species Identification, Abundance and Distribution Determination

3.4.2.1  Species Identification

The Prawns collected from the sampling sites were sorted into various species on the field and collected into an iced cooler and transported to the laboratory where they were preserved in 4% formalin and further identification of specimens was done by checking the length of the rostrum in relation to the antennal scale, chelae color and size, exoskeleton pigmentation and presence or absence of whitish maxillipeds, using standard identification keys ( Powell, 1985 and 1987; Marioghae, 1982 and 1987; Maciel et al.,2011.

3.4.2.2 Species Distribution and  Abundance Determination

Distribution of the prawns was determined by utilizing the variety of nets and gears to actively fish for species from different zones of the rivers around the sampling stations. The variety of nets and traps deployed were the drag nets, scoop nets, non-return valve traps as previously stated. The salinity of the sample stations from where the prawns were collected was noted and the values used to determine the distribution of the Prawns in the sample areas.

Abundance of the Prawn species in the various sample stations was also determined by the Relative Abundance (RA)   method (Negi and Sheetal, 2013). This method, the Relative abundance (RA) of individual species was calculated using the following formula: Number of specimens of particular species x100/Total number of specimens of all.

  1. RESULTS

4.1  Field Salinity Regime

The Salinity of the sample stations as shown in Table 1, through the study period revealed that, Station A (Isiokpo) recorded 0 ppt and is therefore fresh. Stations B (Aluu) and C (Choba) are Oligohaline, having recorded 0ppt to 1ppt, and 1ppt to 4ppt, respectively. Station D (Rumuokparali) recorded between 10ppt and 14ppt; Station E (Ogbogoro) recorded between 14ppt and 16ppt making the both sample sites Mesohaline (5- 18ppt). Station F (Bakana) recording between 16ppt and 18ppt, fluctuated between Mesohaline and Polyhaline, while the Station G (Isaka) where the Bonny River is linked to the Station F (Bakana) section of the New Calabar River is similarly Polyhaline with salinities between 20ppt and 25ppt.

Table 1: Field Salinity regime, showing Variation of Salinity in the Sample Stations in the New Calabar and Bonny Rivers.

Salinity (ppt) / Week

Stations

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

A

Isiokpo

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

B

Aluu

0

0

0

0

0

0

0

0

1

1

1

1

1

1

1

1

0

0

0

C

Choba

1

1

1

1

2

2

2

2

2

3

3

4

4

4

4

4

3

3

3

D

Akpor

10

10

10

10

10

12

12

12

12.5

12

12

13

13

14

14

13

13

12

12

E

Ogbogoro

14

14

14

14

14

14

14

14

16

16

16

16

15

15

15

15

15

14

14

F

 Bakana

16

16

15

16

16

16

16

15

15

18

18

18

18

18

18

16

16

16

16

G

Isaka

20

20

20

20

20

20

20

20

20

22

22

22

25

25

25

25

20

20

20

4.2 Prawn Species Identified, their Distribution and Abundance

4.2.1 Species Identified and their Distribution

The Prawn species identified in the various sample stations were M. equidens, M. macrobrachion, M. vollenhovenii, M. felicinum and M. dux.

The distribution revealed that; the M. equidens were collected at Isaka creek in the Bonny River in salinities ranging from 15ppt to 24ppt.

The M. macrobrachion were collected in the New Calabar River. They were collected in salinities ranging from 0ppt to 15ppt.

The M. vollenhovenii were also collected from the New Calabar River but at nights only, in salinities ranging from 0ppt to 16ppt. Both the M. vollenhovenii and M. macrobrachion species share the same distribution/salinity range and occur together in the same area, but each species is more abundant at different times of the day, with the M. macrobrachion in the day and the M. vollenhovenii at night time.

The M. felicinum was collected from the New Calabar River in hard fresh waters of 0ppt to 1ppt, and finally, M. dux was collected in clear (fresh) waters of 0ppt, in Isiokpo area, in the New Calabar River.

Also, the distribution exhibited by the prawn species as shown in figure 2 below revealed that, the M. equidens occupied the highest salinity (Polyhaline) waters, followed by the euryhaline M. vollenhovenii and, M. macrobrachion, sharing the fresh to brackish (Oligohaline to Mesohaline) mid-waters, while the stenohaline freshwater M. felicinum, and the M. dux occupied the lowest salinities (Oligohaline to Freshwaters).

Macrobrachium species distribution

                                                                  (M. equidens)            +++++++++++++++++++++++++++

+++++++++++++++++++++++++++++++++++++++++++++           (M. macrobrachion)

+++++++++++++++++++++++++++++++++++++++++++++++++ (M. vollenhovenii)

+++ (M. felicinum)     

+ (M. dux)

0    1    2      3      4     5    6     7      8    9   !0     12    13    14   15     16   17 18   19   20 21  22  23  24

                                     Salinity Gradient (ppt)                                                                                     

Figure 2: Distribution of the Macrobrachium Species (Macrobrachium species (M. equidens, M. macrobrachion, M. vollenhovenii, M. felicinum and M. dux) in the Salinity Gradient of the New Calabar and Bonny Rivers.  

4.3  Prawn Species Abundance

The result of the species abundance through the study period (Figure 3) revealed that; in station A, M. dux recorded 100%, while every other species recorded 0%. In station B, M. felicinum exhibited the highest abundance (40.17%), followed by M. macrobrachium (31.98%) and then M. volenhovenii (27.88%), while M. equidens and M. dux recorded 0% each (being absent). In station C, the highest abundance recorded was 47.06 % by M. macrobrachium, followed closely by the M. volenhovenii with 46.84% and M. felicinum with 6.10%, while M. dux and M. equidens recorded 0%. In Station D, M. volenhovenii had 48.01% closely followed by the M. macrobrachium that recorded 48.87%, while the other 3 species (M. felicinum, M. dux and M. equidens) recorded 0% abundance.  Abundance in Station E showed the absence of M. felicinum and M. dux, both of which recorded 0%, while M. macrobrachium recorded 5.94%.   M. equidens with 43.21% abundance showed an increase in abundance but the most abundant was M. volenhovenii with 50.85%.  In Station F as recorded in Stations E, M. felicinum and M. dux recorded 0%. M. macrobrachium was the lowest with 2.64%. The M. volenhovenii was slightly higher with 10.98%. However, the M. equidens recorded the highest with 86.38%.         Finally, in Station G, the M. equidens recorded 100% abundance and every other species were absent (0%).

Figure 3: Abundance of Macrobrachium Species in Sample Stations A to G in the New Calabar and Bonny Rivers.

V.   DISCUSSION

This study reveals that the Salinity of the Isaka area in the Bonny River is Polyhaline. This polyhaline nature of the area could be attributed to the fact that this area is in close proximity to the Atlantic Ocean and there is an intrusion of Sea water. Information on this area of the Upper Bonny River is scarce. However, Babatunde et al. (2013), working on the Abonnema wharf section of the Upper Bonny River, directly linking the Isaka section revealed that, the Isaka section of the Bonny river system is characterized by the interaction of an estuarine and highly saline water located seaward.

In the case of the New Calabar River, it exhibits a Salinity gradient as it gradually increases in salinity from its headwaters where Isiokpo and Aluu are freshwaters, to an Oligohaline Choba section, and then to Mesohaline waters of Rumuokparali, through Ogbogoro to Bakana. This is a variation in Salinity is a unique characteristic feature of the New Calabar River. This observation was in agreement with the findings of Erondu (1983), Dienye and Woke (2015) and Ibim et al. (2016). It is believed that the influence of run-offs and other domestic waters and rains create a dilution of the headwaters while the lower areas in closer proximity with the Sea from the Atlantic Ocean have higher salinities. Also, the higher Salinity experienced in the Bakana section of the New Calabar River can be as a result of their interconnection, leading to the intrusion of Sea water. Dublin-Green, (1990), reported that the New Calabar and Bonny Rivers are connected at the Bakana /Abonnema wharf/Isaka axis of the Niger Delta Wetland. The Salinity gradient pattern recorded  from the Isaka to the Isiokpo in both rivers is similar to the findings of Lirman and Cropper, Jr.(2003), in their study on Salinity fields within Biscayne Bay, in the USA, where a clear salinity gradient was found; with lower, variable salinity occurring in the western margin of the bay due to freshwater inflow from canal discharge and runoff, and higher; and more stable salinities in the eastern margin occur, where oceanic influences are stronger.

All the Macrobrachium species were observed to vary in their distribution and abundance in relation to the salinity in the field. The high abundance and distribution within the salinity gradient of 15ppt to 24ppt for the M. equidens in this study showed that they are stenohaline brackish water species.  This finding is similar to the finding of Powell (1987), who reported the distribution/salinity range for the species in the Niger Delta Area, Nigeria, as ranging between 15ppt and 30ppt. Also in this study, as in the findings of Powell (1986 and 1987) in the Niger Delta, the M. equidens were not found below 15ppt into freshwaters. Similarly, Short (2004), reported that Macrobrachium equidens in its indigenous area of the Indo-Pacific Region is able to inhabit rivers and estuaries.  Contrarily, Maciel et al. (2011), reported that the species which were introduced to the Amazon coast of Brazil, in the Atlantic coast of South America were tolerant to a considerable variation in salinity, ranging from freshwater to 40ppt. Unlike in this study, they were seen to be euryhaline species, as they were reported as hyper- and hypo-osmotic regulators (Denne, 1968 in Maciel et al., 2011). The reason for the difference in distribution/salinity range in this study is not known, but Powell (1987) suggested that, physico-chemical parameters such as temperature, oxygen and others could be key as these parameters vary between tropics and temperate regions. Secondly, he observed that inter-specific competition and geographical variation in the species salt preference could be responsible. Competition could be another issue as several other local species exist in the river system. Maciel et al. (2011) reported a few individuals of M. equidens  when M. amazonicum, a local species featured prominently in the captures, and they suggested that competition may have partly accounted for the reduced numbers of M. equidens and M. acanthurus (another local species) in the traps. 

The M. macrobrachion and M. vollenhovenii were observed to be more euryhaline species, as they were abundantly distributed over a wide range of salinity. The M. macrobrachion salinity range of 0ppt to 15ppt in this study is similar to the salinity range of 0ppt to15ppt reported by Powell (1987). However, Marioghae (1982) reported a slightly lower salinity range of 0ppt to 10ppt for M. macrobrachion in the Lagos lagoon, and an upper limit of 12ppt. Similar to the findings in this study Marioghae (1982) reported that the prawns in the Lagos Lagoon migrate from the estuaries to freshwater. Also, Jimoh et al. (2005); in Jimoh et al. (2012), reported that these two species in the Badagry creek thrive in tidal freshwater and low salinity waters up to and a little above 10ppt.  In agreement also, Opeh and Udo (2014), reported the M. macrobrachion prawn species were dominant in Cross river estuaries and its tributaries, and also found in freshwater areas including ponds, lakes, rivers and even in irrigation ditches.  It is therefore, suspected their inability to penetrate higher salinities may not be as a result of salinity tolerance but may be due to other biotic and abiotic factors such as inter-specific competition, especially in the study area, where several other species co-habit the same environment.

The M. vollenhovenii distribution and abundance in salinities ranging between 0ppt to 16ppt in this study was slightly similar to the findings of Powell (1987), who reported its distribution within salinities ranging between 0ppt to 15ppt in the Niger Delta Area. However, in the Lagos Lagoon, Marioghae (1982) reported their abundance and distribution in higher salinity limits of up to 19ppt; while Marioghae and Ayinla (1995) reported even higher upper salinity limits up to 20ppt. Jimoh et al.(2012), in the Badagry creek, also reported higher salinity limits of up to 20ppt, and that the species could also be found in all kinds of freshwaters. Thus, it is suggested that the absence of M. vollenhovenii in this study in higher salinities above 16ppt may not be totally as a result of salinity preference in their area of distribution. Several other factors may be at play. Inter-specific competition may be a major factor. This is more obvious as both M. vollenhovenii and M. macrobrachion species are distributed along the same salinity gradient and in the same sample stations, but each species is more active at different times of the day, with the M. macrobrachion more active in the day and the M. vollenhovenii in the night.

The Macrobrachium dux was highly abundant and strictly distributed in salinity of 0ppt in this study. This was similar to the finding of Marioghae (1987) and Powell (1982, 1985, 1987), that reported their salinity range as clear freshwater streams. Powell (1982) further stated that, M. dux is presumed to be restricted in its distribution inhabiting small rivers and swamp forest waters of tropical Africa. Similarly, Arimoro and Meye (2007), recorded M. dux in the clear water stretch of Orogodo River in the Niger Delta were it exists as a single species of the genus. Mantel and Farmer (1983) reported that, the M. dux prawns cannot hypo-regulate thus they cannot go into higher salinities as other fresh water decapods that enter higher salinities. Therefore they can be said to be clear freshwater species.                                                                                                                 

Though there is paucity of information on M. felicinum, in the field they were recorded abundantly in hard fresh waters of 0ppt to 1ppt, and absent from salinities above 1ppt. This was similar to the finding of Powell (1985), who reported them to be found only in 0ppt, large hard waters with sandy and rocky bottoms. Also in agreement with this study, was the finding of Marioghae (987) who recorded them in non-tidal freshwater.

Thus, the M. dux and the M. felicinum, can be said to be stenohaline freshwater species as they were found distributed abundantly only in salinities between 0ppt and 1ppt.  They were never distributed in brackish sections of the salinity gradient. Gilles and Pequex (1983), reported that the brackish water is the most exacting and stressful aquatic biotope and establishment of crustacean supposes various highly adapted physiological features. This they reported to be carried out by osmo- and ionic regulation, which involves either hypo-regulation or osmo-conforming in higher salinities. These osmo-conforming species can maintain the blood osmolarity at a more or less constant level independent of the osmolarity of the external medium. (Giles and Pequex, 1983; Mantle and Farmer, 1983; Bushdosh and Atlas, 1975; Sandifer and Smith, 1985; Holtschmit and Pfeiler, 1984). These mechanisms determine the penetration of high salinity areas by the crustaceans. It is therefore believed that, M. equidens, M. macrobrachion and M. vollenhovenii hyper and hypo-regulate and even osmo-conform but the M. dux cannot hypo-regulate going into higher salinities as other fresh water decapods that enter higher salinities (Mantel and Farmer, 1983).

Though the reason for the variation in distribution and abundance of all the species within the Salinity gradient is not known, it was reported that in estuarine environments, salinity can be a primary factor inducing changes in fish distribution patterns (Davenport et al., 1975; Ley et al., 1999; In Lirman and Crroper Jr., (2003). Estuary-dwelling species rarely encounter constant salinity levels and so must often cope with large fluctuations, which can lead to significant stress, depending on the species-specific osmoregulatory capacity and behavioral response (Serafy et al., 1997 In Lirman and Crroper Jr., 2003). The variation in distribution can also be associated with numerous abiotic and biotic factors (e.g. temperature, depth, turbidity, predation and competition). According to Lirman and Crroper Jr. (2003), whereas salinity preference can be inferred from field data, separating salinity effects from other abiotic and biotic influences is difficult. They further reported that these factors may combine to define and influence the species-specific distribution patterns observed in the natural habitat.

  1. CONCLUSION

It is therefore concluded that the study area covering Bonny, and New Calabar Rivers in Rivers State exhibit a distinct Salinity gradient, with a higher point at the Isaka area of the Bonny River, decreasing downward via Bakana area of the New Calabar River and further inwards to the Isiokpo fresh headwaters. Secondly, the four known indigenous and one exotic species of Macrobrachium (M. macrobrachion and M. vollenhovenii, M. dux, M. felicinum and M. equidens) are available in these River systems but exhibit wide fluctuations in abundance and distribution along the wide salinity gradient; with the stenohaline M. equidens recorded at the polyhaline Isaka creek, The euryhaline M. macrobrachion and M. vollenhovenii are located at the Oligo- and Mesohaline sections (though they were active at different times of the day). The fresh water Stenohaline M. felicinum and M. dux species are located at the Oligohaline and Freshwater ends.

Thirdly, though the euryhaline M. macrobrachion and M. vollenhovenii are located at the same sections of the gradient they were active at different times of the day. The reason for this however is not known.

Thus, the variation in Macrobrachium species abundance and distribution in the salinity gradient of the study area is suspected to be as a result of interplay between a series of biotic and abiotic factors, besides Salinity alone, as these species in other continents are mostly freshwater and euryhaline species, and so able to penetrate lower salinities (as in the case of M. equidens) or higher salinities (as in the case of M. macrobrachion and M. vollenhovenii).

It is therefore recommended that several studies should be carried out to investigate combined effects of two or more abiotic and biotic factors simultaneously alongside Salinity. This will be beneficial in providing better understanding of the salinity requirement/tolerance and field distribution of the species, improve culture techniques and the management of Prawn fishery along the Bonny and New Calabar rivers, in Rivers State

REFERENCES

  1. Abowei, J. F. N. (2009). Salinity, Dissolved Oxygen, pH and Surface Water Temperature Conditions in Nkoro River, Niger Delta, Nigeria. Advance Journal of Food Science and Technology 2(1): 36-40, 2010 ISSN: 2042-4876 © Maxwell Scientific Organization, 2009
  2. Anetekhai (1989). Salinity tolerance of the African River prawn (Macrobrachium vollenhovenii) (Herklots) in Asejire Lake, Oyo State, Nigeria. Nig J Sci 23: 3133.
  3. Anetekhai (1990). Sexual dimorphism and egg production in Africa River prawns (M. vollenhovenii) (Herklots) from Asejire Lake, Oyo State, Nigeria. Nig J Sci 24: 147-150.
  4. Arimoro, F.O. and, Meye, J.A. (‎2007). Some aspects of the biology of Macrobrachium dux (Lenz, 1910) (Crustacea: Decapoda: Natantia) in River Orogodo, Niger Delta, Nigeria. Acta biol. Colomb., Vol. 12 No. 1, 111–122. www. scielo.org.co/scielo.php?script=sci_arttext& pid=S0120…
  5. Babatunde, B.B., Sikoki, F.D., Onojake, M.C., Akpiri, R.U., and Akpuloma, D. (2013). Heavy Metal Profiles in Various Matrices of the Bonny/New Calabar River Estuary, Niger Delta, Nigeria. DOI: http://dx.doi.org/10. 4314/gjes.v12i1.1 Global Journal of Environmental Sciences Vol. 12, 2013: 1-11 Copyright© Bachudo Science CO. Ltd. Printed in Nigeria. ISSN 1596-6194.
  6. Bello-Olusoji, O.A., Balogun, A.M., Fagbenro, O.A., and Ugbaja, O. (1995). Food and feeding studies of Macrobrachium vollenhovenii. In: Fish and Shellfish Larviculture Symposium. Laverns, P.E. Jaspas, Roelants (Eds) Europ Aquac Soc, Special Publication 24: 1425-1427
  7. Bushdosh, M. and, Atlas, R. M. (1975). Response of two Arctic Amphipods, Gammarus zaddachi and Boeckosinus Conisimus affinis, to variation in temperature and salinity. Journal of the Fisheries Research Board of Canada. vol. 32, No. 12, pp. 2564 to 2568.
  8. Deekae, S.N. and, Abowei, J.F. (2010). The fecundity of Macrobrachium macrobrachion (HERKLOTS, 1851) from Luubara Creek, Ogoni Land, Niger Delta, Nigeria. - International Journal of Animal and Veterinary Advances, 2(4): 148–154.
  9. Dorgello, J. (1976): Salt tolerance in crustacean and the influence of temperature upon it.
  10. Deekae, S.N and, Idoniboye-Obu, T.I.E. (1995). Some aspects of commercially important molluscs and crabs of the Niger Delta, Nigeria. Environmental Ecotoxicology, 13(1): 136-142.
  11. Dienye, H.E. and, Woke, G.N. (2015) Physicochemical Parameters of the Upper and Lower Reach of the New Calabar River Niger Delta. J Fisheries Live st. Prod 3:154. doi:10.4172/2332-2608.1000154        
  12. Dublin-Green, C.O. (1990). Seasonal variations in some physicochemical parameters of the Bonny Estuary, Niger Delta. NIOMR Technical Paper No. 59, Nigerian Institute for Oceanography and Marine Research, Lagos, July 1990, pp: 21-25.
  13. Eniade, A. A. and, Bello-Olusoji, A. O. (2011). Continental J. of Fisheries and Aquatic Science 5 (1): 31 – 37.                              
  14. Enin, U.I. (1995). First estimates of growth, mortality and recruitment parameters of Macrobrachium macrobrachion (Herklots, 1851), in the Cross River Estuary, Nigeria. Dana, 2(1): 29-38.
  15. Erondu, E.S. and, A.C. Chindah, (1991). Variation in the physicochemical features and phytoplankton of new Calabar River at Aluu, Rivers State, Nigeria. NIOMR Technical Paper No. 75, Institute for Oceanography and Marine Research, Lagos, December 1991, pp: 1-18.
  16. Ezenwa, B. (1981). A study on the reproductive biology of the catfish Chrysichthys nigrodigitatus (L) in Nigeria. Ph.D. Thesis, University of Lagos.
  17. George E., Bassey A., Joseph I., and, Ubong G. (2013). The fecundity of brackish prawn (Macrobrachium macrobrachion, Herklots, 1851) from great Kwa River, Obufa Esuk Beach, Calabar, Cross River State, Nigeria. Journal of Biology Agriculture and Healthcare.; 3(11):45-56.
  18. Gilles, R. and, Pequex (1983): Interaction of chemical and osmotic regulation with the environment. Environmental Adaptation, and biology of crustacean, by Dorothy Bliss. Chapter 4, pp. 113 to 162. Vol. 8
  19. Holtschmit, Karl-heinz, and Edward Pfeiler, (1984): Effect of salinity on the survival and development of larvae and post larvae of Macrobrachium americanum, Bate (Decapoda, Paleamonidae) Crustacean 46 (1), E. J. Brill-Leiden.
  20. Jimoh, A. A., Clarke, E.O., Whenu O.O., and Adeoye, H.B. (2009) Food and feeding habits of the African river prawn (Macrobrachium vollenhovenii, Herklots, 1857) in Epe Lagoon, Southwest Nigeria. Inter. J. Fish Aqua. 3: 10-15.
  21. Jimoh, A.A., Clarke, E.O., Whenu. O.O., Anetekhai, M.A., and Ndimele. P.E. (2012) Morphological Characterization of Populations of Macrobrachium vollenhovenii and Macrobrachium macrobrachion from Badagry Creek, Southwest Nigeria. Asian Journal of Biological Sciences; 5:126-137.
  22. Lawal-Are, A.O. and, Owolabi, A.T. (2012). Comparative Biology of the Prawns Macrobrachium macrobrachion (Herklots) and Macrobrachium vollenhovenii (Herklots) From Two Interconnecting Fresh/Brackish Water Lagoons in South-West Nigeria. J Marine Sci Res Dev 2:108. doi:10.4172/2155-9910.1000108.
  23. Lirman, D. and Crroper Jr. (2003). The Influence of Salinity on Seagrass Growth, Survivorship, and Distribution within Biscayne Bay, Florida: Field, Experimental, and Modeling Studies. Vol. 26, No. 1, p. 131–141.
  24. Maciel, C.R.; Quadros, M. L.; Abrunhosa, F.; Bastos, S.; Schneider, H. and Sampaio, I. (2011). Occurrence of the Indo-Pacific freshwater prawn Macrobrachium equidens Dana 1852 (Decapoda, Palaemonidae) on the coast of Brazilian Amazonia, with notes on its reproductive biology. SciELO Analytics, An. Acad. Bras. Ciênc. vol. 83 no.2. http://dx.doi. org/10.1590/S0001-37652011000200013 

  25. Mantle, L. H. and, Farmer, L. (1983). Osmotic and Ionic Regulation. Biology of Crustacean Regulation by Dorothy E. Bliss. Vol. 7, pp 336-341.
  26. Marioghae, I. E. (1982). Notes on the Biology and Distribution of M. vollenhovenii, and M. macrobrachion in the Lagos lagoon. Rev. Zool. Afr. 96, 3.
  27. Marioghae, I. E. (1987). An Appraisal of the Cultivability of Nigerian Paleamonid prawns. ARAC/87/WP/4. UNDP/FAO/NIOMR Lagos. Working Paper, 12pp.
  28. Marioghae, I.E. (1990). Studies of Fishing Methods, Gear, and Marketing of Macrobrachium in the Lagos Area. Nigerian Institute of Oceanography and Marine Research, Technical Paper, No. 53, 20pp.
  29. Marioghae, I.E. and, Ayinla, O.A. (1995). The Reproductive Biology of Macrobrachium vollenhovenii (Herklots, 1857) and Macrobrachium macrobrachion (Herklots, 1851) in Nigeria. ARAC/NIOMR Technical Paper No. 100, 16 p.
  1. Negi, R.K. and, Sheetal, M.  (2013). Species Diversity, Abundance, and Distribution of Fish Community and Conservation Status of Tons River of Uttarakhand State, India. Journal of Fisheries and Aquatic Science, 8: 617-626.
    DOI: 
    10.3923/jfas.2013.617.626 URL: https://scialert.net/abstract/?doi=jfas.2013.617.626
  1. Ngah, A.S., Braide, S. and Dike, C.C. (2017) Physicochemistry of Elechi Creek in the Upper Bonny Estuary, Rivers State, Nigeria. Journal of Geoscience and Environment Protection, 5, 181-197. https://doi.org/10. 4236/gep.2017.58015
  2. Opeh, P.B. and, Udo, P. J. (2014) The culture potential of the brackish river prawn Macrobrachium macrobrachion (Herklots, 1851) reared under three management strategies. Journal of Fisheries and Aquatic Studies 1(3):178-182
  3. Ogolo, S. G., Ugbomeh, A. P. and Isitor, G. N. (2017). Physico-chemical parameters of Iwofe and Bakana Rivers, tributaries of the New Calabar River, Niger Delta, Nigeria. Research Journal of Pure Science and Technology Vol. 1 No. 2 2017 ISSN 2579-0536 www.iiardpub. org
  4. Powell, C. B. (1980). Key to shrimps and prawns (Crustacea: Decapoda, Natantia) of the Niger Delta Basin Development Authority Area. Consultancy Report, University of Port Harcourt, 34.
  5. Powell, C. B. (1982). Fresh and Brackish Water Shrimps of Economic Importance in the Niger Delta. In the Proceedings of the 2nd Annual Conference of Fisheries Society of Nigeria (FISON), Calabar 2527 Jan; 1982. p. 254-285.35.
  6. Powell, C. B. (1983). Fresh and Brackish water shrimps of economic importance in the Niger Delta. In: Proceedings of the 2nd Annual Conference of the fisheries society of Nigeria (FISON), Calabar, 25–27. January, 1982, p. 254–285.
  7. Powell, C.B. (1985). The Decapods Crustaceans of the Niger Delta. In: Wilcox, H.B.R. and C.B. Powell, (Eds.), Publication Committee, University of Port Harcourt, pp: 226-238.
  8. Powell, C.B. (1986). Occurrence of the Indo- Pacific prawn Macrobrachium equidens in West Africa (Crustacea, Decapoda, Palaemonidae). Rev. Hydrobiol. Trop. 19(2): 75- 79.         
  9. Powell C. B. (1987). Occurrence of the Indo- Pacific prawn Macrobrachium equidens in West Africa. (Crustacean, Decapods, Paleamonidae)
  10. Rogers, S., Allen, J., Balson, P., Boyle, R., Burden, D., Connor, D., Elliot, M., Webster, M., Reker, J., Mills, C., O’Connor, B., and Pearson, S. (2003).Typology for Transitional and Coastal Waters for UK and Ireland Report. Ukseamap 2010 Interactive Mapping portal, Salinity layer help, jncc.defra.gov.uk
  11. Sandifer, P. A. and, Smith, T. I. J. (1985). Fresh water prawns chap. Crustaceans and mollusk aquaculture in the U.S. Edited by Jay V. Hunter and E. Evan Brown.
  12. Sandifer, P. A. and, Smith, T. I. J. (1985). Hardness and alkalinity P. 85 to 86. Crustaceans and mollusk aquaculture in the U.S. Edited by Jay V. Hunter and E. Evan Brown.
  13. Sandifer, P. A. and, Smith, T. I. J. (1985). Salinity. Crustaceans and mollusk aquaculture in the U.S. Edited by Jay V. Hunter and E. Evan Brown.
  14. Short, J.W. (2004). A Revision of Australian River Prawns, Macrobrachium (Crustacea: Decapoda: Palaemonidae). Hydrobiologia 525: 1-100.         

 

 



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