Spawning Potential Ratio of Feather Back ( Chitala Lopis ) at Kampar River , Riau

The feather back, Chitala lopis is an important economic fish, inhabit Kampar River and its population tend to decrease so that management and conservation efforts should be conducted. Limited data of the feather back is one of the problems in formulating the management of the population. Spawning potential ratio (SPR) approach is an option being used in the management of the fish stock in the poor data. The study aimed to analysis spawning potential ratio of the feather back in Kampar River, Riau. The research has been conducted in May, August and October 2016. The total length at first capture (Lc) of feather back was less than the total length at first maturity (Lm) with the SPR value of 5 %. This condition could impact to decreasing the feather back stock. The SPR value should increased more than 30 % so the feather back population would been stable. Regulation of the fisheries was mainly limited mesh size of the gillnet operated should be applied.


Introduction
Kampar River have a huge diversity of fish species, of which 58 species are found in Kampar Kanan (Fithra & Siregar, 2010) and 86 species are found in Kampar Kiri River (Simanjuntak et al., 2006).The distribution of this species include Borneo, Java and Sumatera (Haryono, 2008).Feather back in Kampar River is important economically value but it's species in endangered status (Aryani, 2015).Stock of feather back in Kampar River was divided into two stocks zona, namely in upstream and downstream.The Feather back in Kampar River also shows different genetic characteristics with these species from Musi and Barito Rivers (Wibowo & Marson, 2012).Feather Back is carnivore fish and can utilize fish juvenile, shrimp, insect, worm, benthos and plant as natural food (Burnawi, 2009;Wibowo, 2014).For the optimize and sustainable of harvest it need conservation and management for this species.This objectives of fish resource management is to optimize the production of harvest while maintaining the sustainability of resources, without over exploitation, and maintaining of stock health and also improving stocks condition (Cope & Punt, 2009).In generally, fisheries resource management is based on stock biomass and biological parameters of target fish (Wiedenmann et al., 2013;Carruthers et al., 2014).its model requires catches data on several years, the abundance of fish at a certainly age and the life cycle of target species (Deroba & Bence, 2008), whereas the data about feather back fisheries in Kampar River is limited (poor data).Secondary data as production, number of fishing gear and trip, and number of fishermen in time series are not available.The approach that can be usage to determine the status of fisheries and formulate management with limited data (MacCall, 2009) can be done based on biological parameters ie infinity length, growth constant and length at first mature and length frequency (Wayte & Klaer, 2010).The approach for feather back stock management with limited data with Spawning Potential Ratio (SPR) (Prince et al., 2011).SPR can be used as a basis for consideration in fisheries management with poor data (Hordyk et al., 2015a).SPR is the proportion of mature gonadal fish that is not exploited in capture activity (Prince et al., 2011).The objective of this research was to analyze spawning potential ratio as basic management and conservation of feather back stock at Kampar River, Riau Province.

Research location
The study was conducted in Kampar River, Riau Province at May, August and October 2016.Feather Back samples were obtained from fisherman catches at Pelalawan and Batu Sanggan locations and fish landing at Terata Teratak Buluh (Figure 2).Fishing gear were used include hook, gillnet and trap.The total length of the fish was measured using a measuring board with a precision of 0.1 cm and the weight of the fish was weighed using a scales with 100 g accuracy.Secondary data as production of fish was obtained from the Marine and Fisheries Agency, Riau Province.The Growth parameter as K and t o were obtained from desk study (Sani, 2010).The data of length frequency and maturity stage for male and female were obtained from Wibowo (2010).

Growth patterns
Growth pattern for feather back was analyzed using length-weight relationship with equations: For L ∞ estimation was calculated with Wetherall (1986) approach by the following steps: 1.The dete i ti f west i it f the fish e gth ge was calculated by the equation: Where: F = Total length frequency of fish ̅ = Middle total length of fish n = Number of fish with total length is larger than ' ' = Lower limit value of total length 2. Regression between ̅ -' de g Where:

Length at first catch and mature of fish
Length at first catch of father back was calculated using cumulative frequency curve (Beverton & Holt,1975)  The length of first mature (L m ) was calculated using logistic curve (King, 2007) with formulation as: Where: P = Proportion of fish mature (%) L m = The total length at stage mature of fish (cm) L = Total length of fish (cm) R = Slope

Spawning potential ratio
Spawning potential ratio (SPR) provides a conservation strategy to maintain the reproduction of a stock that is useful in preventing overfishing recruitment (Slipke et al., 2002).SPR methods are commonly used in the management of fish resources (Goodyear, 1993;Ault et al., 2005;Prince et al., 2015).Its can be used to define reference points for datapoor fisheries (Thorson et al., 2012).The SPR value is calculated based on Huo et al., (2015) equation as follows:

Estimated for length at first capture with optimally economic value
Estimation length of first capture with optimally economic value was calculated based on King (1995) approach.The calculation was done with some steps as: 1. Determination of fish length at age t (L t ) (Sparre & Venema, 1999) Where:

Result and Discussion
The efforts of freshwater fisheries management are constrained due to the limited information about capture of fish, the size of the fish caught and fish stocks) (Suuronen & Bartley, 2014).Management of fish resources can be done by setting the season and location of the capture, the number of catches and the size of the fish that can be captured (Andersen et al., 2018).The biology aspects of fish can be a reference in fisheries management, for example in determining the rules for fishing (Zhou et al., 2012) based on the Spawning potential ratio (Hordyk et al., 2015b).Total length and weight of feather back was catch in this research around 31,0-98,0 cm and 200-8.200g espective y.It's w s ge th feather back that was catch at Riam Kanan Reservoir with total length and weight around 14-74,5 cm and 100-3300 gr respectively (Umar & Kartamihardja, 2007).
The Feather back fish were capture during the study ranged from 31.0-98.0cm with a weight ranging from 200 to 8,200 g.It was greater than the fish caught in Riam Kanan Reservoir, which range between 14-74.5 cm with a weight of 100-3300 g (Umar & Kartamihardja, 2007).The length-weight relationship of female and male respectively follow the equation W = 0.0006L3,6269 with value R2 = 0,9299 and W = 0.0008L3,5705 with value R2 = 0,9216 (Figure 3 Growth patterns for male and female of feather back at Kampar River shown positive is et ic p≥0,05 .Its indicated that the increasing of the weight of fish was faster than increasing of length.The result was same with Lestari (2010) report, which was isometric positive for feather back with b= 3,4612.
The average total length of fish was as an indicator of fish stock health (Klaer et al., 2012).Length data more informative for fisheries management (Ono et al., 2015).The cumulative frequency of the total length was captured during the study that presented in Figure 4.The most dominant total length was caught in this research were 55-60 cm for female and 60-70 cm for male.The total length was greater when it compared with the results of the study from Lestari (2010) namely around 40-55 cm.The asymptotic length (L oo ) of feather back was estimated from the total length data frequency caught in the Kampar river 107.5 cm for 12,400 grams of weight.The asymptotic length of this study was when compared with Sani (2010) report was 96,1 cm.The length of exploited fish data and biological parameters of fish can be the basis for determining fish resource management) (Kokkalis et al., 2015).
Estimates of the total length at the first capture (L c ) for female and male fish were 45 and 53 cm, respectively.The size of the first mature (Lm) for female was 68 cm (Figure 5).The Lm value for Chitala lopis species is greater than Notopterus notopterus species with a total length of 13.5 cm for male and 16.2 cm for female fish (Gustomi et al., 2016).These feather back spawning during the rainy season around November-February (Wibowo & Sunarno, 2006).The total length size of the first fish caught (Lc) was smaller than the size of the first fish matured gonad (Lm).Its continuously could caused pressure of feather back population so that caused no recruitment.The length at fish maturity can be the basis for determining the size of fish that can be caught so that it will ensure continuity of recruitment (Myers et al., 1999;Cope & Punt, 2009;Conn et al., 2010).The Lc value must be greater than the Lm value (Babcock et al., 2013;Ambrose & Udo, 2015).Rest icti g fishi g the sp w i g p pu ti wi w t th t fish th t su vived until the start of the spawning period will be allowed to spawn (Overzee & Rijnsdorp, 2015) thus ensuring stability and the number of fish populations (Cid et al., 2014).Management of fish resources based on SPR requires information on Lm (Midway & Scharf, 2012).
The SPR value at the first captured (L c ) was 5% while 30% of SPR value could been reached if the catch was in the length of fish after matured (L m ) (Figure . 6).The SPR method is a method used in the determination of the length of the Exploitative Portunus pelagicus Linnaeus, 1758 in Belitung (Ernawati et al., 2015) and red drum in the Atlantic Ocean (Vaughan, 2002).Figure 6.SPR Graphic and age of feather back at Kampar Riau Based on L m value showed that feather back was capture before spawning and caused recruitment overfishing.SPR value must be greater 30% for maintain of sustainability population.Fish resources Management in the Hawaiian Islands also determinate by SPR value > 30% (Nadon et al., 2015).The effort for its in Kampar River as regulation of fish size for captured by limiting of mesh size of gear (Wibowo et al., 2010;Erisman et al., 2014), so that capture of fish with longer than 80 cm.Restrictions on the size of fish that can be caught based on the value of the SPR are efforts of fish resources management (Klaer et al., 2012;Arlinghaus et al., 2010;Katselis et al., 2010).The SPR can be a reference in determining of maximum sustainable yield (Legault & Brooks, 2013) and prevent overfishing (Hordyk et al., 2016).Hal ini This related with sustainability of recruitment (Huo et al., 2015).Spawning stock is maintained so that the fish can reproduce before being caught (Froese et al., 2008;Wolf et al., 2015) and increased reproductive potential resulting from protection (Wilson et al., 2013).Exploitation of fish resources based on the SPR value is expected to be able rebuilding overfished stock back to sustainable level (Hordyk et al., 2015c) with revised reference points for exploitation (Cadrin & Pastoors, 2008 Regulation of fish caught will provide optimal economic value (Eikeset et al., 2013).Well-managed fisheries resources will provide optimal economic value (Dowling et al., 2008).Fishing carried out on) SPR 30-40% should result in high yield with minimal risk of collapse d c t ibute t ebui di g f ve fished stocks (Midway & Scharf, 2012).The highest economic value occurs when the harvest was done at tot e gth f fish ≥ 80 c average fish weight around 3.5 kg (Figure 7).Fish populations will decline gradually due natural mortality, which caused by predation or environmental degradation.The number of individual fish caught will be more if the exploitation is done less 80 cm of total length but the total biomass will become smaller.If exploitation is done at larger 80 cm the fish biomass will be optimal and economic valued too.This can happen because the caught fish has a larger individual size so that the total catch rate will be higher (Svedang, 2015).

Conclusion
The dominance of total length feather back was captured smaller than the length at first mature with SPR value was 5%.To ensure of fish populations sustainability, SPR value must be greater than 30%.This could be achieved if the total length of the exploited was 80 cm.In addition, exploitation at this total length also provides the optimal economic value for fisherman.

Figure 3 .
Figure 3. Length-weight relationships of feather back fish at Kampar River

Figure 5 .
Figure 5.The mean total length at first mature (L m ) of feather back