V.N. Pillai and N.G. Menon

Marine

Research and Management

Editors

V.N. Pillai and N.G. Menon

Central Marine Fisheries Research Institute

(Indian Council of Agricultural Research) Tatapuram P.O., Cochin-682 014

Kerala, India

2000

38

ABSTRACT

The marine catfish production showed a continuously de- clining trend all along the Indian Coast, from 67,666 t (1982) to 37,518 t (1995), while the situation is alarming along the SW a n d SE coast.

This group is one of the most vulnerable resources for irrational harvest during their migratory and breeding phase. With the ad- vent of mass harvesting gear like purse seine and trawlers, there has been a continuous onslaught on this resource during the peri- ods of south bound or north bound migrations parallel to the coast.

The damage is further aggravated when their spawning shoals are exploited from the surface often causing large scale destruc- tion of parents and egg / embryos, leading to overfishing affect- ing the recruitment to the population. The paper gives the possible migratory route, seasons of vulnerability and impact of fishing gear on the resources. It is attempted to corelate the surface drift with

the seasonal migrations. Various management practices are proposed to conserve the threatened species and suggested possible lines of exploitation preferably on the non-migratory soecies from distant waters in the middle shelf.

Introduction

The marine catfish is a commercially i m p o r t a n t ground fish distrib- uted widely in the coastal waters and formed a s u b s t a n t i a l fishery resource of the country till eighties. In view of its importance in the marine fish production a n d the future potential, the CMFRI h a s initiated a re- s e a r c h project in seventies and regularly monitored the fishery, biology a n d

stock c h a r a c t e r i s t i c s for evolving m a n a g e m e n t strategies. The all India catfish production showed a continuously declining t r e n d with the p e a k in 1982 (67,666 t) a n d the dip in 1992 (36,165 t). The a n n u a l average catfish

Marine Fisheries Researcli and Management

catch in the pre-mechanised era was less t h a n 20,000 t. The large scale m e c h a n i s a t i o n in 1971- 1980 witnessed a hike in the landings to the t u n e of 51,271 t followed by the p u r s e seine fishing in K a r n a t a k a and Kerala which h a s further p u s h e d the landings to 57,860 t in 1981-1985 period.

Thereafter the production slowly declined to 4 0 , 0 0 8 t in 1991-1995. But the revalidated potential is a r o u n d 123,000 t from the EEZ, of which less t h a n 50 m depth zone holds 60,000 t and above 50 m 6 3 , 0 0 0 t (Anon., 1991).

Menon et ah, (1996) estimated the potential from t h e zone between 50 and- 100 m a s a r o u n d 4 0 , 0 0 0 t and 5 7 , 0 0 0 t from 0-50 m depth, based on d a t a from the experimental bottom trawling (1985-1994) of, FORV sagar sampada.

On the contrary, the earlier estimate of potential yield of catflshes was 3 1 0 , 0 0 0 t (George et aJ., 1977). The highly varying potential estimate made during different periods of time together with declining landing t r e n d s necessitate the implementation of suitable m a n a g e m e n t strategies all along the coast, for s u s t a i n i n g the catfish fishery for the future.

The last 4 decades catfish fishery h a s been critically analysed and evaluated to s t u d y whole g a m u t of the over exploitation problem for de- veloping m a n a g e m e n t options to protect and conserve the t h r e a t e n e d

species from further degradation. Considerable r e s e a r c h i n p u t h a s gone Into this group and the work of Mojumdar (1969, 1978); Dan (1977, 1980);

Krishnamoorthi (1978); Menon (1979), Silas et al (1980); Mojumder and Dan (1981); Dhulkhed etal (1982 a, b); Rao et al. (1977); Anon. (1987) Menon et.

al (1989,1992 a, b , 1996); J a m e s et al. (1989) are worth mentioning in this context.

Data base

Regionwise, Statewise and gearwise catfish landings and effort data col- lected by the NMLRDC (Anon, 1969; FRAD, 1979, 1981, 1986,1995) and spe- cies composition a s well as biology, behaviour and population characteris- tics d a t a of d o m i n a n t species from selected centres are utilised for the p r e s e n t study. S t a n d a r d m a n a g e m e n t tools have been made u s e of in suggesting conservation and m a n a g e m e n t m e a s u r e s along the whole range of its distribution.

Fishery

All India catch: Till the beginning of m e c h a n i s a t i o n the resource was exploited by various a r t i s a n a l gears from shallow g r o u n d s during

fair w e a t h e r . The a n n u a l average (1956-66) catfish catch of 2 1 , 1 3 9 t (2.8 % of the total m a r i n e fish landings of the country), was realised by glUnets, hooks & line, b o a t seines, shore seines and other a r t i s a n a l gears. Sev- eral species c o n s t i t u t e d the fishery, with the peak landings in post and p r e m o n s o o n m o n t h s , and the production showed s t e a d y i n c r e a s e ' over the years. When mechanised fishing (trawlers) gained strength in 1966-1975.

the catfish landings also made c o n c u r r e n t progress with a n n u a l average of 2 9 , 5 2 7 t (1966-1970) and 57,776 t (1971-1975). The introduction of p u r s e seine in 1976-1980 period and its popularisation in 1980 - 1985, along the s o u t h w e s t coast h a s helped to progress the a n n u a l average landings to the t u n e of 5 7 , 8 6 0 t (1980-85). The harvest w a s a t its peak during 1971 - 1 9 8 5 by a m u l t i t u d e of competing u s e r s , which include a r t i s a n a l fishers, mecha- nised and motorised small scale fishers and the i n d u s t r i a l sector. The period of a b u n d a n c e of catfish is J a n u a r y - J u n e off M a h a r a s h t r a Coast, April- September off K a r n a t a k a a n d Kerala, J u l y - September In the Gulf of M a n n a r a n d March - J u n e and December - J a n u a r y off the A n d h r a Coast.

The r e s o u r c e is chiefly exploited by m e c h a n i s e d trawlers (33 %) followed by m e c h a n i s e d gill n e t t e r s (21 %), n o n - m e c h a n i s e d gear (14%), p u r s e seine (11%) hooks & line (10%) and dol n e t (5%). Indiscriminate exploitation of juvenile a n d s u b - a d u l t p o p u l a t i o n s by bottom trawlers a n d b r o o d e r s /

s p a w n e r s by p u r s e seiners h a s resulted in poor recruitment, spawning stock decline a n d infrequent shoreward migrations. Ultimately the production gradually declined in 1986-1990, t h o u g h several innovative gears contrib- uted towards the coastal fisheries in this period, with a n a n n u a l average catch of 5 1 , 2 4 4 t. The landings further declined to 4 0 . 0 0 8 t in 1991-

1995 i n s p i t e of extended fishing to deeper ground u p t o 80 -100 m d e p t h a n d species r e p l a c e m e n t s .

The west coast landed 69.7 % of the total catfish catch a n d t h e east coast 30.3 %. Until 1980 the s o u t h w e s t coast was the d o m i n a n t catfish pro- ducing region (56.2 % of the total catfish landing of the west coast); w h e r e a s d u r i n g 1981 - 1 9 8 5 period, the n o r t h w e s t coast produced 72.5 % a n d in

1991-95 more t h a n 9 5 % of the catfish catch of west coast (Fig.l). T h u s , the depletion of the catfish stock is well manifested in the s o u t h w e s t region,

comprising K a r n a t a k a a n d Kerala, where the landings declined from 2 4 , 7 0 2 t (1971-75) to 1212 t (1991-95). The landing in the n o r t h w e s t region (Goa, M a h a r a s h t r a and Gujarat) registered a continuously increasing t r e n d from a n a n n u a l average of 7 3 6 0 t (1956-1966) to 26,269 t (1986-1990). In the

Marine Fisheries Research and Management

90000

80000

70000

60000

59 62 1965 68 71 74 77 1980 83 86 89

Figure 1 Regionwise annual catfish production trend.

92 95

n o r t h w e s t region the trawl n e t l a n d e d 3 8 % of t h e total catfish c a t c h , followed by gill net (25 %), p u r s e seine (16%), dol net (8%), hooks & Une (7%) and non mechanised gear (7%). The trawlers contributed 37% of the total catfish catch of s o u t h w e s t region, gill n e t t e r s landed 2 3 %, p u r s e seine 19 %, hooks

& line 12 % and n o n - m e c h a n i s e d gear 6%.

The catfish landings in Gujarat showed a progressive Increase from 1843 t (1967) to 14,541 t in 1994 (Fig.2) Tachysurus dussumieri (45 %), T.

tenutspinis (16%), T. caelatus (12%), T. thalassinus (12 %) and Osteogeneiosus militaris (8%) were the most common species. Stock a s s e s s m e n t s t u d i e s of T. tenuispinis and T. thalassinus revealed t h a t the p r e s e n t level of their exploitation is slightly high for the MSY a n d hence proposed a 2 5 % reduction in fishing p r e s s u r e , especially by n o n selective g e a r s . The p r o d u c t i o n of M a h a r a s h t r a showed a steady and progressive increase with the peak in 1988 (21,086 t) a n d there after the landings fluctuated between 7461 t (1995) a n d 15,279 t (1994) (Fig.3). Of the several species occurring in the fishery the d o m i n a n t were T. dussumieri (25 %), O. militaris (22%), T. thalassinus (19%) and T. tenutspinis (14%). At Goa till 1989 the production increased

^ ^ " 5 8 2 ^

16000, 14000 12000

« 10000 I 8000 h 6000r

NM

DOL

H&L

I

'f Gillnet

Trawl

1956

0.00 20.00 40.00 Percentage

Fig. 2 Annual production trend of catfish in Gujarat and their gearwise production.

gradually a n d reached 5 3 1 7 t a n d thereafter decUned to 82 t in 1994 (Fig.4).

The rise In l a n d i n g s Is linked directly to p u r s e - s e i n e Impact (1976-1990) a n d exploitation of shoaling species of T. tenuispinis, T. dussumieri a n d T. serratus.

MAH

1956 60 64 68 72 76 80 84 88 92

Fig. 3 Annual production trend of catfish in Maharashtra and their gearwise pro- duction.

Marine Flaheries Research and Management

other OB P

NM 1 H&LH

p s l ^

Gillnetll^

Trawl i f

0.00

m

Y" —

50.00 100.00 Percentage

1969 72 75 78 81 84 87 90 93

Fig. 4 Annual production trend of catfish in Goa and their gearwise production.

The a n n u a l landing of 3 1 9 3 t (1956) h a s increased progressively and reached a peak of 10,253 t (1982) in K a r n a t a k a (Fig .5). The landing declined thereafter until 1988 a n d recorded a steep fall to 49 t in 1993.

The catch chiefly composed of T. tenuispinis, (53 %), T. dussumieri, (31%), T.

serratus, (10%) and T. t\ia.\assinus (6%) during 1979 - 1988. Thereafter (1992- 1994) the former 2 species declined \^.dussumieri 1 1 % and T. serratus, 5 %), while the, T. thalassinus continued to contribute to the fishery with 65 % of the total catfish catch. In Kerala the landings showed a fluctuating progress with the peak of 3 3 , 5 2 8 t in 1974 and this trend continued

tf) 0) c c 0 H

1956 60 64 68 72 76 80 84 88 92 ^

Fig. 5 Annual production trend of catfish in Karnataka and their gearwise production.

"584"

1956 6 0 6 4 6 8 7 2 7 6 8 0 8 4

Fig. 6 Annual production trend of catfish in Kerala and their gearwise production.

T.thalassini T.tenuispini

T.serratus T. dussuwieri

Fig. 7 s p e c i e s w i s e catfish production at Cochin.

-C585;>

Marine Fi»herie« Research and Management

s

1

4 0 0 0 0 0 3 5 0 0 0 0 :

3 0 0 0 0 0 V

2 5 0 0 0 0 1 2 0 0 0 0 0 '•:/ '

1 5 0 0 0 0 ^ 1 0 0 0 0 0 K

5 0 0 0 0 \^j^m

1981 _{8 3}

•

85

•

87 8 9

S^T. tenuspinis

|<^;^a2a^^222^^^ T.dussumiarl

•mm.1 ' * — - r n - | ; r r - p j t t i i , | „ a i n t j g T. serratua

91 93

Fig. 8. Specieawiae catfish production at Calicut.

until 1983 (15,344 t) a n d thereafter declined with wide fluctuation u p t o 1988 (Fig.6), The catch diminished steeply from 1989 a n d reached a meagre 3 0 8 t in 1995. The species composition h e r e d u r i n g 1984-1988 w a s T.

thalassinus (40%), T. tenuispinis (30%), T. serratus, (18%) a n d T, dussumieri, (12%); w h e r e a s in 1991-1995 t h e composition showed t h e domi- n a n c e of, T. t h a l a s s i n u s (65%) and T. serratus, (19%). The specieswlse landings from Cochin and Calicut clearly illustrate the stock depletion of T.

tenuispinis. and T. dussumieri (Figs. 7 and 8).

Along the s o u t h e a s t region the landings progressively increased upto 1975 (8,190 t) a n d thereafter declined to 2129 t in 1986-1990; w h e r e a s in the n o r t h e a s t region the production Increased steadily a n d reached a peak in 1981-1985 (13,283 t) a n d thereafter m a i n t a i n e d steady l a n d i n g s . In 1981-95 period t h e NE region c o n t r i b u t e d a b o u t 81 % of t h e total catfish c a t c h of e a s t coast. During 1991-1995 t h e b u l k of t h e c a t c h (38 %) from the NE w a s landed by gill-netters followed by n o n - m e c h a n i s e d gear (24 %), trawl n e t (20 %), a n d h o o k s & line (17 %). Whereas in the s o u t h e a s t region the m e c h a n i s e d trawlers landed 47 % of the total catch; t h e n o n - m e c h a n i s e d gear c a u g h t 38 % followed by gill-netters 12%.

Catfish production from Tamil Nadu registered a general increase until 1982, 3 3 9 6 t in 1956-65 to 8 0 5 5 t in 1971-75, with fluctuation and declined thereafter (7031 t i n 1976-80 to 1907 t i n 1986-90, (Fig.9).Although many species are available in this p a r t of the coast, the d o m i n a n t species are

(0 0

c c 0 h

Gillnet Trawl i

O.OO 20.00 40.00 60.C Ptrcenbga

Fig. 9. Annual production trend of catfish in TamilNadu and their gearwise production.

T. thalassinus (30 %). T. caelatus. (18 %). T. dussumieri (4 %), T. serratus (3 %) a n d O. militaris (2 %). Catfish catch a t Pondicherry showed a declining

trend 184 t (1965-75) to 81 t (1976-85) a n d it further declined thereafter (except a s u d d e n hike in 1986 - 1043 t). (Fig. 10). . The landing showed a general increasing trend 2542 t (1956-65) to 8 5 7 4 t (1971-75), till 1 9 8 1 - 1985 and thereafter slowly declined with minor fluctuations along A n d h r a Coast (Fig. 11). The major species c o n t r i b u t e d to the fishery were, T.

H&L

Glllmt

Tnwl

0.00 10.00 20.00 30.00 40.C Parccnlag*

91 93 95 "-

Fig. 10, Annual production trend of catfish in Pondicherry and their gearwise production.

Marine FtsherieB Research and ManKgement

thalassinus (67 %) a n d T. tenuispinis (32%) d u r i n g 1 9 6 0 - 1 9 7 5 period;

w h e r e a s the latter species declined to less t h a n 10 % of the total catfish catch in 1990-1995 period. Stock a s s e s s m e n t s t u d y (Menon et al., 1992) revealed t h a t t h e effort s h o u l d be r e d u c e d c o n s i d e r a b l y to achieve

s u s t a i n a b l e yield of T. thalasstnus and T. tenuispinis. The landings in Orissa registered a fluctuating trend with general Increase (Fig. 12.); the

H&L

Gillnet

Trawl

0.00 20.00 40.00 60.00 Percentage

Fig. 11 Annual production trend of catfish in Andhra Pradesh and their gearwise production.

(0 0)

c c 0

h

8000- 7000^

6000 5000 4000 3000 2000;

1000

A

tipLn.4.-A

H&L

Gillnet

Trawl

40.00 Percentage

1976 78 80 82 84 86 88 90 92 94

Fig. 12 Annual production trend of catfish in Orissa and their gearwise production.

cmr:?

p e a k l a n d i n g w a s in 1981 (6084 t) a n d it formed 12.5 % of t h e total m a r i n e fish c a t c h of the s t a t e in 1981-1985. Of the several species occurring T.

thalassinus, T. dussumieri, T. tenuis pints, T. s o n a , T. caelatus, a n d O.

milttarts are t h e major species contributing to the fishery. In West Bengal t h e catch showed a peak of 9 0 7 5 t in 1982 a n d thereafter it w a s s t a b l e

a n d formed a b o u t 17 % of the total m a r i n e fish catch of the s t a t e in 1986- 1990 (Fig. 13.). The dominant species are, T. thalassinus. T.Jella, T, caelatus a n d O. militaris. Large quantities of T.Jella young fish l a n d i n g w a s reported from the b a g n e t operation in the Hoogly- Matlah area.

(A « c c 0

h

1976 78 80 82 84 86 88 90 92 94

Fig. 13 Annual production trend of catfish in West Bengal and their gearwlse production.

Depthwise production

Catfish landing d a t a of trawl for t h e year 1997 a n d 1998 were utilised to s y n t h e s i s e the distribution / a b u n d a n c e p a t t e r n in b a t h y m e t r i c r e a l m s of 0-

10, 10-20, 2 0 - 3 0 , 30-40, 40 -50 a n d above 50 m in various maritime s t a t e s and all along t h e Indian Coast, In all India m e c h a n i s e d trawl yield of cat- fishes, a b o u t 39 % was from above 50 m depth, 37 % from 3 0 -50 m a n d the rest from the inshore realm u p t o 30 m. In the NE region, t h e depth zone 30 -

"589"

Marine Fl«herie» Retearch and Management

50 m landed 58 % and the i n s h o r e 10-20 m produced 47 % of t h e total catfish catch; w h e r e a s the NW yielded more t h a n 50 % from above 50 m depth zone a n d a b o u t 2 5 % from 40 -50 m (Fig. 14).

ai997 rVig98

0 10 20 ^0 40 Percentage of catch

Fig. 14 Bathymetrlc production (trawl) of catfish (percentage).

50

Fishing impact a s s e s s m e n t

Trawl Net: During the pre-mechanised period the catfish fishery was s u s t a i n e d by Indigenous crafts a n d n o n - m e c h a n i s e d gears s u c h a s hook &

line, gill net a n d b o a t seine a n d t h e production showed a g r a d u a l a n d steady improvement, with many species contributing to the fishery. The Introduction of trawl net in fifties and large-scale popularisation in s u b - s e q u e n t decades altogether changed the fishing p a t t e r n a n d production t r e n d s in many of the maritime S t a t e s . This s h r i m p targeted b u t non- selective gear landed m a n y species of demersal fishes in large q u a n t i t i e s a n d catfish w a s one of the Important Items among t h e by c a t c h . Invariably the bottom trawls catch composed of bottom living juvenile a n d s u b - a d u l t , and medium size column moving 1-2 year old fish. Often the juvenile and s u b - a d u l t s of 7-20 cm formed the bulk (numerical) of the landing a t most of the centres along s o u t h w e s t a n d s o u t h e a s t coasts. The Impact of this bottom

sweeping h a s c a u s e d damage not only to the ground fishes sustainablllty.

b u t also to the bottom h a b i t a t a n d the biota (epi- a n d in fauna) which form the prey for demersal fishery resources {Lakshmi and Rao, 1992;Menon ,1996).

The landings of, T. thalassinus, by trawlnet consisted of less t h a n one year old and i m m a t u r e ( 7-20 cm) fish to the t u n e of 80% at Mangalore (1988-1991) and 83 % at V l s a k h a p a t n a m (1986-1993). Similarly a b o u t 70 % of the trawl catch of T. tenuispinis , consisted of j u v e n i l e s / s u b - a d u l t s (13.5 - 2 3 cm) a t M a n d a p a m (1988-91) a n d 88 % a t Mangalore ( 1983-89) often from a trawling depth within 30 m. This type of juvenile fishery from the n u r s e r y g r o u n d s h a s caused both recruitment and growth overfishing, preferably of T. thalassinus and T. tenuis pints.The coastal trawling along Mangalore d u r i n g 1983-93 clearly showed almost complete d i s a p p e a r a n c e of T. tenuispinis , from the fishery (Fig. 15). The destructive, overfishing of

T. tenuispinis, by bottom trawling along Andhra Coast h a s been reported earlier by Krishnamoorthi (1978), Dan (1980), Anon., (1987), Menon et al, (1992 a a n d b ) a n d Lakshmi a n d Rao (1992).

Purse seine: The introduction of p u r s e seine into the commercial fish-

Ul O

T.tenuispinis iassinus rratus

T. dussumien

Fig. 15 Specieswise catfish catch by trawl net at Mangalore 591

Marine Flgherie» Research and Management

Ing in 1979 and its intensification in 1980s h a s accelerated the growth of coastal pelaglcs a n d few shoaling demersals production along Goa, Karnataka and later in Kerala. This h a s paved the way for rapid proliferation of the gear a n d the effort h a s reached a r o u n d 400 u n i t s in Mangalore alone with a c o n c u r r e n t high production of 4 2 8 6 t of catfish in 1982. Invariably the p u r s e seine catch consisted of gestatlng m a l e s / female shoaling spawners of T. tenuispinis, T. dussumieri, a n d T. serratus, d u r i n g t h e p e r i o d s September-November , December - March and J u l y - September respectively (Table 1 ). In 1979- 87 period the gestatlng males (T. tenuispinis and T. dussumieri) alone formed 64 % of t h e catfish c a t c h by p u r s e seine.

The estimate of a n n u a l destruction of egg / embryos / larvae of T. tenuispinis TABLE 1: P u r s e s e i n e l a n d i n g of c a t f i s h b r o o d e r s

embryo

/ eggs /

Year Month Area Catch of Egg/ Larvae References Brooders (t)

T. tenuispinis

1980 September Mangalore 2 0 4 . 9 16.0 t Silas etal, 1980

1980 October. 2 4 1 . 5 14.0 t Silas etal, 1980

1980 October Gangoll 8 2 . 0 7.6 t Silas etal, 1980

1981 1982 1982 1982 1982 1982 1982 1982 1983 1984 1986

Mangalore No d a t a

September. Karwar 136.1 3.9 t

October. Karwar

September Mangalore 10.2 October. Mangalore 4 7 5 . 6 October. Mangalore 3 3 1 . 0 September Mangalore 9.0 September Gangoll 1094.0

"592"

2.3 t

0.13 million 5.9 million 1.7 mlHion 0.05 million 2.5 million

D h u l k h e d et al,

D h u l k h e d et al,

D h u l k h e d et al.

T. dussumieri 1983

1985 1984 1986 1987

March

J a n u a r y . Feb.-Mar February T. serratus

1996 October

Mangalore 2 1 . 0

Mangalore 68.7 Mangalore 8 4 9 . 0 Malpe 2 5 . 4

Cochin ^4.5

1.65 l a k h s M u t h i a h & Rao 1985

5.7 million 0.38 million

280 Kg.

during the above period is a b o u t 8.2 million (13.4 t) by p u r s e seine. If allowed to grow a n d contribute to t h e fishery (by age 2 y e a r s a n d above) it would have yielded 2 7 6 8 t per year (assuming 10 % n a t u r a l mortality).

Similarly the estimated a n n u a l fishing mortality of eggs / embryos / larvae of, T. dussumieri, by p u r s e seine in t h e above period is 1.6 million (5 t).

The loss by way of this fishing mortality of egg / larvae is equivalent to 3320

QL O

T. dussumieri Ljtenuispinis

^.serratus T.thalassinus

Fig. 16 Specieswise catflsh catcli by purse seine at Mangalore.

Marine Fisheries Research and Management

t of exploitable fish (4 -5 years old and above) after allowing a 10 % n a t u r a l mortality. The w a n t o n destruction of catfish brooders with eggs / embryo by p u r s e seine h a s been reported from K a r n a t a k a since 1980 a n d the vul- n e r a b l e species were T. tenuispinis, T. d u s s u m i e r i and T. serratus ( Silas et al, 1980; Dhulkhed elal. 1982 a a n d b ; Muthiah and Rao. 1 9 8 5 ) . The

p u r s e seine catch per unit effort d a t a of Mangalore during 1982-92 shown in Fig. 16 clearly indicates the total d i s a p p e a r a n c e of b o t h T. tenuispinis and T. dussumieri from this part of the coast since 1989 a n d 1991 respec- tively as a consequence of m a s s destruction of egg/ embryos by p u r s e seine.

Biology and behaviour

The characteristic reproduction, shoaling behaviour and migration of m a n y species of marine catfishes made them easy target for over- e x p l o i t a t i o n . S p e c i e s s u c h a s T. tenuispinis, T. dussumieri a n d T.

serratus although demersal denizens of coastal h a b i t a t s , exhibit shoaling behaviour a n d vertical and horizontal migration especially during their adult / breeding / s p a w n i n g p h a s e s of life history. All t h e s e species have low fecundity ranging from 2 5 - 190 ova and with a single spawning in a year.

The breeding period lasts a r o u n d 5 m o n t h s with peak in 1-2 m o n t h s (Sep- tember - November for T. tenuispinis, December - J a n u a r y for T. dussumieri.

a n d J u l y - August for T. serratus). They are easily vulnerable to p u r s e seines in this period. All species exhibit p a r e n t a l care with the male carrying the brood (25 - 120 eggs) in the oro-buccal cavity for 1 to 2 m o n t h s time until the juveniles ( 4 - 7 cm) are released. After spawning t h e brooding males segregate into s h o a l s a n d move along the surface a n d prefer shallow wa- ter. The newly released Juveniles of all species of t a c h y s u r i d s live in the shallow muddy g r o u n d s feeding on the bottom epl- a n d in- fauna. (Mojumder a n d Dan, 1981; Mojumder, 1969; Menon, 1979; Anon., 1987; Lakshml and Rao, 1992). The i n c e s s a n t bottom trawling in these g r o u n d s frequently harvested large quantities of both the prey, benthic fauna a n d the preda- tor catfishes and i m m a t u r e demersal fish j u v e n i l e s / s u b - a d u l t s . The char- acteristic shoreward breeding migration, the low fecundity, oral incubation a n d the shallow n u r s e r y g r o u n d s are the biological and behavioural char- acteristics detrimental to their survival when threatened by fishing mortal- ity.

Migration

The predominantly demersal marine catfishes exhibit d i u r n a l vertical migration [Rao et al... 1977) and horizontal migration towards t h e coast and parallel to the coast during monsoon (James e t a l . , 1989). The s e a s o n a l yield trends, bumper landings at various fish landing centers from Ratnagiri to Madras (Chidambaram, 1987; Srinivasarengan, 1988; Nammalwar etal..,

1989: S u n i l k u m a r et .al..1993; Sawant, 1994 a n d Kemparaju et al, 1995) throw considerable light on the probable season a n d course of migration of the major shoaling species T. tenuispinis, T. dussumieri a n d T. serratus.

Analyses of d a t a revealed a s o u t h b o u n d coastal migration s t a r t i n g from Ratnagiri d u r i n g Southwest monsoon, c o n c u r r e n t with the surface drift p a t t e r n in t h e Arabian Sea and n o r t h b o u n d migration in the Bay of Bengal u p t o 15 ° N In August- S e p t e m b e r a n d thereafter t h e reversal t r e n d in Northeast monsoon (November -January) (Figs. 17 a n d 18). The shoreward m i g r a t i o n of s h o a l s is mostly evident d u r i n g b r e e d i n g s e a s o n a n d t h e

n^

MEAN SURFACE CIRCULATION S.W. MONSOON (—^)

Fig. 17 Seasonal surface drifts and the migration pattern of catfishes during SW Monsoon

C 5 9 5 ^

Marine ri»herie» Research and Management

* 0 ^ l T O * »o* ^fK>'

X3£

MEAN SURFACE CIRCULATION N.E. MONSOON (—^)

Fig. 18 Seasonal surface drifts and the migration pattern of catflshes during NB Monsoon

migration parallel to the coast Is reported from below 17° N a t west and 15°

N at" east coast. The m a s s h a r v e s t of brooders / s p a w n e r s h a s , therefore, often t a k e s p l a c e from t h i s p a r t of t h e c o a s t . T h i s h a s r e s u l t e d in r e c r u i t m e n t overfishing a n d d e p l e t i o n of s t o c k s of T tenuispinis

a n d T. dussumieri, in s o u t h w e s t and s o u t h e a s t sectors a s evidenced by a continuously declining production trend since late eighties and nineties.

Whereas the stocks of the northern sectors (Northwest and Northeast) remain Isolated, a n d the breeding stocks are not t h r e a t e n e d by m a s s exploitation a n d h e n c e continue to c o n t r i b u t e to the fishery. The s o u t h b o u n d drift a n d c o n c u r r e n t movement of catfish, bull's eye a n d ribbonfish s h o a l s are reported to a p p r o a c h the coast a r o u n d 17 ° N a n d move down (James et al.,. 1983; Vljayakumarn and Naik, 1988). The movement could be traced u p t o Madras in t h e e a s t a n d a reverse movement in Northeast monsoon.

T h e c i r c u l a t i o n p a t t e r n d u r i n g t h e S o u t h w e s t a n d N o r t h e a s t m o n s o o n (Varadacharl a n d S h a r m a , 1967; J a m e s et.al., 1983) clearly shows t h a t

the monsoon c u r r e n t flow is s t r o n g from 17° N d o w n w a r d s d u r i n g SW monsoon a n d in t h e n o r t h b o u n d Northeast monsoon ( November - J a n u - ary) the drift w e a k e n s a n d partly moves away from the coast a t a r o u n d 17°

N in the west coast. The movement of the above resource also follows the s a m e p a t t e r n . However, to prove t h i s hypothesis, further investigation is needed by conducting tagging recovery, drift bottle and racial s t u d i e s of migratory species.

Management

A critical analyses of the d a t a on the fishery, biology a n d behaviour of t a c h y s u r i d catflshes in the last 4 decades provide valuable r e s e a r c h i n p u t s for a s s e s s i n g and evaluating the stock c h a r a c t e r i s t i c s a n d for developing s u i t a b l e m a n a g e m e n t strategies. The earlier a s s e s s m e n t of its potential (George et al, 1977; Anon.. 1987; Menon et al, 1992 b , 1996) together with stock a s s e s s m e n t s t u d i e s give a dismay p i c t u r e of c o n t i n u o u s l y declining potential for t h i s resource.

The dwindling production a n d poor r e c r u i t m e n t along the s o u t h w e s t a n d s o u t h e a s t region now d e m a n d implementation of regulations s u c h as b a n n i n g coastal bottom trawling, controlling p u r s e seining of gestatlng / spawning stocks, etc. All s u c h m e a s u r e s are detrimental to the economic

objective of the i n d u s t r y and therefore liable to resist. Therefore, it should first b e decided t h a t w h e t h e r the short term economic gains should take preference over the affirmed policy of achieving a s u s t a i n a b l e yield whereby protecting the resource from over exploitation. In t h e interest of

both, it Is therefore, necessary to formulate s u i t a b l e m a n a g e m e n t s t r a t e - gies for each region / maritime State depending on the m a g n i t u d e of the problem.

The problem of fishery m a n a g e m e n t regulations are severe a n d com- plex in tropical country like India where the marine c a p t u r e fisheries is multlspecies and the resource u s e r s belong to multlsectors a n d n o t easy to Implement a n d enforce owing to political or socio-economic r e a s o n s . Here

t h e fisheries m a n a g e m e n t is viewed a s a cost, w h e r e a s due to lack of m a n a g e m e n t , often there is over crowding, over investment a n d over capitalisation in the fishing Industry. This excess cost is invariably born by Government and the c o n s u m e r s . In s u c h a context fisheries m a n a g e - m e n t h a s become a benefit a n d therefore should be considered a s a priority

' 5 9 7 '

Marine Fisherio Research and Management

for future development. With the p r e s e n t s t a t e of scientific knowledge on fish s t o c k s , blotic and abiotic d a t a b a s e , p a s t experience on resource behaviour, additional research i n p u t , together with skilled and rationale fisherfolk's p a r t i c i p a t i o n , it would be possible to achieve s u s t a i n a b l e fisheries r e s o u r c e s m a n a g e m e n t and conservation.

The Impact of trawling a n d p u r s e seining on the collapse of North Sea herring fishery, with the longest record of s u s t a i n a b l e exploitation, pros- ecuted with drift n e t s , is a historic example in this context. Similarly the vulnerability of Capelln {Mallotus villosus) to over exploitation d u e to its peculiar reproductive and shoreward migratlonal behaviour a n d the collapse of its fishery h a s a close resemblance with the p r e s e n t situation of catfish brooder devastation in our country. The collapsing herring fishery and In- s h o r e capelln fishery were subjected to severe restriction on fishing effort or b a n n e d their fishing for period of 2 - 5 years following a c r a s h of their fishery. These restrictions have helped the stocks to recover and increase the spawning stock b l o m a s s (FAO, 1992).

The regionwise production d a t a clearly show t h a t the i n p u t of mecha- nisation (trawling a n d p u r s e seining) was responsible for s u d d e n increase m landings in 1970 - 1985 periods. Simultaneously this fishing h a s also c a u s e d damages to shoaling species like, T. tenuispinis, and T. dussumieri, by way of growth overfishing (trawlnet impact) a n d r e c r u i t m e n t overfishing (purse seine I m p a c t ) . As the spawning stock migrations are pronounced in the s o u t h w e s t region, the effect of overfishing is felt at a n alarming m a g n i t u d e in t h i s region. Earlier s t u d i e s revealed t h a t m a n y c o m m e r c i a l l y I m p o r t a n t s p e c i e s a r e u n d e r h e a v y f i s h i n g p r e s s u r e (Krishnamoorthl, 1978; Dan, 1977 , 1980; Anon., 1987 ; Menon, 1979;

Menon et al, 1992 a and b; Bensam and Menon, 1994).Accordlngly they suggested regulatory m e a s u r e s (species specific / gear specific / region spe- cific) for implementation by the concerned maritime S t a t e s . But, often the regulatory m e a s u r e s were not Implemented due to several socio-economic / political r e a s o n s .

Because of the oceanographlc isolation of n o r t h e r n stocks from s o u t h - ern stocks it would be worthwhile to propose different m a n a g e m e n t s t r a t e - gies for the n o r t h e r n and s o u t h e r n regions. The non- mechanised / motor- Ised sector fishing by drift / gill n e t s a n d hooks & line should be encour-

aged and promoted all along the distributional range of this resource (Menon etal, 1989). This socially equitable proposition will help to s u s t a i n the re- source harvest. Mechanised bottom trawling should be controlled or b a n n e d in the coastal sector u p t o 30-m depth all along the coast a n d t h e unbridled entry of OB mini trawlers should be regulated. These regulations will

r e d u c e growth overfishing a n d therefore, gradually help to e n h a n c e the stock. The control or b a n on this bottom trawling operation will also reduce benthic fauna devastation and the exploitable resource's feeding h a b i t a t deg- radation (Lakahml a n d Rao, 1992; Bensam a n d Menon, 1994; Menon, 1996).

The catch a n d landing of spawning stock and gestating males by p u r s e seine s h o u l d be b a n n e d totally all along the distributional r a n g e ; t h i s could be easily achieved since the skilled fishermen can detect the cat- fish s h o a l s a n d avoid fishing them during breeding s e a s o n . The implemen- tation of this regulation, of course with the beneficiary fisher societies participation, will reduced the egg/ larval destruction and hence improve a n d s t r e n g t h e n r e c r u i t m e n t (James etal, 1989; Menon, 1996). As the spawning of T. tenuispinis, T. dussumieri and T. serratus mostly teikes place in the coastal h a b i t a t of Kerala - K a r n a t a k a , this regulation should be effectively imple- mented in the s o u t h e r n sector, where this shoreward migrations are i n t e n s e .

It is often reported t h a t stocks of catfishes occur in a r e a s beyond 50 m depth for exploitable concentration (Joseph and J o h n , 1987; J a m e s et at,

1989; J a m e s a n d Plllai, 1990; Menon, 1996). But the existence of s u c h stock in deeper g r o u n d s is restricted to certain s e a s o n s / periods of time, depending on the feeding biology a n d behaviour of the species a n d the prevailing o c e a n o g r a p h i c conditions (Rao et al., 1987). However, t h e p r e s e n t commercial catch d a t a (1992-1994) revealed t h a t more t h a n 90 % of the total catfish catch is realised from less t h e n 50-m depth zone insplte of the extension of fishing into deeper grounds u p t o 100 m. Therefore, to make fishing regulations more economical, it would be worthwhile to harvest them during t h e shoreward migration p h a s e by selective gears w i t h o u t causing r e c r u i t m e n t or growth overfishing, r a t h e r t h a n to resort to a more costly fishing in the deep. However, the resource could be Judiciously harvested from the fishing g r o u n d s beyond 30 m depth by High Speed Demersal Trawl (HSDT) or midwater trawl net along the regions where shoreward migration are s c a n t y or Infrequent.

Marine Fi»herie» Research and Management

C u r r e n t production of a b o u t 3 6 , 0 0 0 t from the n o r t h e r n region (NW and NE) could be further improved by responsible fishing by non-selec- tive gears (Hooks & line, gill nets) and by midwater trawling in 30 - 100 m, for a s u s t a i n a b l e yield, from the potential available in t h i s p a r t ( more t h a n 80% of the current total catfish potential from the Indian EEZ). It is generally agreed t h a t unbridled open access to any easily vulnerable resource is the major o b s t a c l e to s u s t a i n a b l e a n d r e s p o n s i b l e fisheries m a n a g e m e n t (Gordon, 1954). Therefore it is imperative t h a t the entry should be restricted through i n p u t controls or o u t p u t controls, of course through persuasive societal participation, to achieve the MSY.

Acknowledgment

The a u t h o r s gratefully acknowledge the encouragement from Dr. M.

Devaraj, Director, CMFRI, Cochin.

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