1 Introduction

The Red Sea, an almost land-locked northern branch of the tropical Indian Ocean is one of the most remarkable repositories of biological diversity on the globe. The Red Sea ichthyofuna is quite well known compared to other parts of the tropical indopacific ocean. Khalaf and Disi (1997) recorded 1,280 fish species from this semi-enclosed northern extention of the Indian ocean. Sixteen nemipterid species are recorded from the Red Sea. This family consists of the genera nemipterus, scolopsis and parascolopsis (Randall, 1983). Fishes of family nemipteridae represent one of the most commercially important fish groups in the trawl fishery of the Gulf of Suez, Red Sea. Many authors studies Nemipterus species such as (Bakhsh, 1996; Rajkumar et al., 2003; Manojkumar, 2004; McIlwain et al., 2006; Kerdgari et al., 2009; Ramadan, 2010, Joshi, 2010; Amine, 2012).

The present study was carried out with the aim of investigating the abundance of globiform kidney in the various fishes in family nemipteridae in Red Sea. After discovering the accessory globiform kidney by EL-Halfawy and Ramadan (2014) in N. japonicus used as a new method for identifications of the different species. Also, used this a new organ as a method in the reproductive index.

2 Materials and Methods

Random samples of family nemipteridae catch landed at the Attaka harbor during the fishing season from September 2010 to May 2011 were collected monthly. The samples were identified by FAO (1990), to differentiate between species (four nemipterus species N. japonicus, N. virgatus, N. zysron and N. mesoprion) and S. ghanam (genus Scolopsis).

Monthly length and weight were determined for the collected species for the two common species N. japonicus and N. virgatus. The fishes were dissected, then gonads and accessory globiform kidney were removed and weighted to the nearest gm. The monthly gonadosomatic index and kidnosomatic index were calculated as respectively as:

GSI = weight of gonad (g) / gutted weight of fish (g)×100

KSI = weight of accessory globiform kidney (g) / gutted weight of fish (g) × 100

3 Results and Discussion

Fishes of family nemipteridae representing one of the most commercially important groups in the trawl fishery of the Gulf of Suez, Red sea. Six species, belonging to two genera were recorded in the Gulf of Suez (Breikaa, 1996). These are N. japnicus, N. bipunctatus, N. zysron, S. vosmeri, S. ghanam and S. taeniatus. The threadfin breams N. japonicus is the most abundant fish species catch. It considered about 90% of nemipterid landing followed by the slender threadfin breams N. zysron that contributes about 7% of the landing while the other four species appear occasionally in the catch (El-Ganainy and Mehana, 2003).

In the present study, the species, which obtained from genus nemipterus was four species N. japonicus, N. virgatus, N. zysron and N. mesoprion (Figure 1), according to the FAO catalogue, 1990 (Morphologically). The first two species are common in catch while the other two species were collected in v0poery few numbers. The only species, which obtained from genus Scolopisidsis was S. ghanam which found also in few number and not considered important in nemipteridae catch. Therefore, this study not agreement with the (Breikaa, 1996 in the presence of other species of family nemipteridae like N. bipunctatus, S. taeniatus and S. vosmeri in our region. Besides the morphological differences in the species by color filament and size (Figure 1). Our study differentiated between the two genera, which found in our region, by the presence or not of accessory globiform kidney (Figure 2). This accessory globiform kidney embedded in the flesh at the beginning of caudal portion in four species of genus nemipterus. While in genus scolopisidsis (S. ghanam), which represented the region, this accessory globiform kidney not present. Therefore, the presence of accessory globiform kidney is specific for genus nemipterus and considered as a new method to differentiate between these two genera in Red Sea.

In the previous study in N. japonicus elucidated that, the accessory globiform kidney changed in size and weight by sex and maturation (Ealhalfawy and Ramadan, 2014). In male, this accessory globiform kidney was cleared and large in size and weight (Figure 2), but in female N. japonicus very small and its weight nearly constant 0.02 g. This change of globiform kidney were found in all four species which included in this study from nemipterus but due to the small number which obtained from N. zysron and N. mesoprion not helped us to completed the reproductive studies. The present studies not conformed to results obtained from EL-Ganiny and Mehana (2003) which mentioned that N. zysron represented 7% of nemipterid catch in Attaka harbor.

Therefore, this study included the two common species N. japonicus and N. virgatus which found in a large number and were present monthly during the fishing season, which extended from September to May in our region.

Gonadosomatic index (GSI) of N. japonicus and N. Virgatus

The gonadosomatic index for two species studied began to decrease in September for N. japonicus for male and female (0.5 for male and 3.6 for female) (Figure 3;  Figure 4). Gonadosomatic index of females was higher than that of male and follow nearly the same pattern for both sexes.  The spawning season takes place from May to September. The results obtained confirmed with results obtained from EL-Halfawy (1995) and Ramadan (2010) on N. japonicus, which stated that, N. japonicus has a short spawning season that occur in summer season.

The monthly changed of GSI value of male and female N. virgatus were shown in Figure 5 and Figure 6. The average values showed variations during the period from September 2004 to May 2005 recording that the maximum value in October for both male and female (0.5 for male and 3.8 for female) followed by a progressive decrease from November to March and slightly stability from March to May. So, the maturation may be starting in months of the prohibition of fishing  and the spawning season for N. virgatus  may be extend from September to December.

Kidnosomatic index (KSI) in male N. japonicus and N. virgatus

From this study and the previous on N. japonicus and N. virgatus, the investigations showed that, this accessory globiform kidney variable with sex in female of both species nearly unchangeable but in male of both species changeable with maturation. So, in this study, used the kidnosomatic index as a new method and indicator to maturation and spawning for male only.

KSI of male N. japonicus, recorded highest values during September 0.42 (Figure 7), then began to decrease during October to February and nearly increased and steady from March to May 0.25, 0.3 and 0.3 respectively. On the other hand, KSI for N. virgatus (Figure 8) revealed that the maximum value obtained in October 0.45 and gradually decreased occurred from November to February and slightly increase and case of stability from March to May. From the previous results, GSI and KSI of male's N. japonicus and N. virgatus, have the same manner. Both indices emphasize that spawning season extend during summer season for N. japonicus and from September to February for N. Virgatus.

Figure 7 Monthly distribution of kidnosomatic index for male Nemipterus japonicus during the fishing season(Sep. 2004 to May 2005)

4 Conclusion and Recommendation

From the present investigations we can concluded that:

1) There is a new method for identification the genus nemipterus of family nemiptridae from other genera of the same family, besides the morphological difference by the presence of accessory globiform kidney which specific for Nemipterus sp,.which collected from Red sea.

2) Using this new organ as a new indicator for maturation and spawning for male of Nemipterus sp. only than female.

The above-mentioned lead to encourage to put the following recommendations:

3) It must be studies the physiological of this accessory globiform kidney to know its relation to maturation of male only.

4) Complete the differentiation between the other genera of family nemipteridae by the presence of this accessory globiform kidney in different regions.

Acknowledge

Praise to ALLAH, the lord of the universe, by whose grace this work has been completed. Our special thanks are appreciating to our colleagues, who helped us during the preparation of this work and for their supporting especially Dr. Nasser S. Abd EL-Rahman.

Reference

Amine A. M., 2012, Biology and assessment of the thread fin bream Nemipterus japonicus in Gulf of Suez, Egypt, Egypt. J. Aquat. Biol. & Fish., 16 (2): 47–57

Bakhsh A.A., 1996, The Biology of Thread Bream, Nemipterus japonicus (Bloch) from the Jizan region of the Red Sea. Journal of King Abdulaziz Univeristy of Marine Science, Special Issue Symposium on Red Sea Marine Environment Jeddah, 7: 179-189

Breikaa M.I.M., 1996, Dynamics and fisheries management of the threadfin bream Nemipterus japonicus (Pisces: Nemipteridae) in the Gulf of Suez. Ph. D. Thesis, faculty of science, University of Cairo

EL-Ganainy A.A., and Mehana S.F., 2003, Resource assessment and management prospective of two nemipterid species (Nemipterus japonicus and N. zysron) in the Gulf of Suez. Bull. Nat. Inst. Of Oceanogr. & Fish., ARE, 29: 15-29

EL-Halfawy M.M., 1995, Studies on the reproduction of thread fin bream Nemipterus japonicus in Gulf of Suez, Master’s Thesis, Faculty of Science, Suez Canal University

EL-Halfawy M.M. and R A.M.amadan, 2014, Accessory Kidney of Threadfin Bream Nemipterus japonicus and Their Relation to Gonad Maturation, International Journal of Aquaculture, 4: 79-84

FAO species catalogue, 1996, volume 12

Joshi K.K., 2010, Population dynamics of Nemipterus japonicus (Bloch) in the trawling grounds off Cochin . Indian Journal of Fisheries, 57(1): 7-12

Kerdgari T., Valinassab S., Jamili M.R., and Kaymaran F., 2009, Reproductive biology of the Japanese Threadfin Bream, Nemipterus japonicus, in the Northern of Persian Gulf. Journal of  Fisheries  and Aquatic Science, 4 (3): 143-149

http://dx.doi.org/10.3923/jfas.2009.143.149

Khalaf M.A., and Disi A.M., 1997, Fishes of the Gulf of Aqaba, published by the marine science station, Aqaba, Jordan

Manojkumar P., 2004, Some aspect on the biology of Nemipterus japonicus (Bloch) from Veraval in Gujarat, Indian Journal of Fisheries, 51: 185-191

McIlwain J., Hermosa G.V., Claereboudt M., Al-Oufi H.S., and Al-Awi M., 2006, Spawning and reproductive patterns of six exploited finfish species from the Arabian Sea, Sultanate of Oman, Journal of Applied Ichthyology, 22: 167–176

http://dx.doi.org/10.1111/j.1439-0426.2006.00723.x

Rajkumar U., Narayana-Rao K., and Jose-Kingsly H., 2003, Fishery biology and population dynamics of Nemipterus japonicus (Bloch) off Visakahapatnam, Indian Journal of Fisheries, 50: 319-324.

Randall J. E., 1983, Red sea reef fishes. PP. 183. Immel Pub. London.

Ramadan A.M., 2010, Reproductive biology and histological features of female thread fin bream, Nemipterus japonicus, in Gulf of Suez, Egypt, Journal of Aquatic Research, 36(3): 493-500