Stock assessment of whiting (Merlangius merlangus euxinus nordmann) along Bulgarian Black Sea Coast during 1976- 1993 Prodanov K., Daskalov G. Dynamique des populations marines Zaragoza : CIHEAM Cahiers Options Méditerranéennes; n. 10 1995

(1)

Stock assessment of whiting (Merlangius merlangus euxinus nordmann) along Bulgarian Black Sea Coast during 1976- 1993

Prodanov K., Daskalov G.

Dynamique des populations marines Zaragoza : CIHEAM

Cahiers Options Méditerranéennes; n. 10 1995

pages 73-75

Article available on lin e / Article dispon ible en lign e à l’adresse :

--- http://om.ciheam.org/article.php?ID PD F=95605406

--- To cite th is article / Pou r citer cet article

--- Prodanov K., D askalov G. Stock assessmen t of wh itin g ( Merlan giu s merlan gu s eu xin u s n ordman n ) alon g B u lgarian B lack Sea Coast du rin g 1976-1993. Dynamique des populations marines . Zaragoza : CIHEAM, 1995. p. 73-75 (Cahiers Options Méditerranéennes; n. 10)

---

http://www.ciheam.org/

http://om.ciheam.org/

(2)

WHITING (MERLANGIUS MERLANGUS EllXINUS NORDMANNI ALONG BULGARIAN BLACK SEA DURING 1976-1993

Kamen PRODANOV and Gueorgui DASKALOV"

Department of Marine Biology,Institute of

'Department of Ichthyology, Institute Fisheries,VAREA IBulqaria) The catches of whiting are obtained with trapnets and also it appears as bycatch in the sprat fishery with the bathypelagic trawl. All this embarrasses the correct determination of the actual catches (Pro- danov,1984), on account of which the whiting has always been conside- red a's a poorly exploited fish (Domashenko and Serobaba,l990).The lar- gest catches have been realized by Turkey-the mean catch during 1984

-

1991 is 20.46 thousand tons. Length composition of these catches \:a-

ried from to cm, while the Bulgarian catches ranged whitin cm.

Material and Methods

Whiting biomass during 1976-1993 was calculated by VPA (Mesni1,1989) and length converted cohort analysis (LCOH0R)- Sparre,1987. The

respectively the values of Fst for sprat are accor- dlng r 19 83, 1.989) and Daskalov's (1993) data. As it was mentioned, the whiting catches are realized mainly as a bycatch in the sprat flshery. That is we used the sprat values for although the whiting i s demersal fish, while the sprat is mudfish. Besides, the oldest age groups of whiting ( 5 and 6 years old) keep away from the shore in contrast sprat. whose fishery i s going on in the coastal zone

-

25-40 m depth. HaLTing in mind all these differences consider that the assessment made have to examine as an attempt for determi- ning the margin stock of whiting along Bulgarian Black sea coast.

Results and Discussion

table 1 the results from VPA and LCOHOR are represented. It ap- that, t h e assessments obtained by the a b ~ \ ~ e mentioned methods differ from one another mainly during 1990-1991. Accordiq to VPA and LCOHOR analyses the initial and mean biomasses of whiting had varied from 27273.6 tons (1976) to 10893.4 tons (1988) and from 16072.3 tons

(1978-1979) to tons (1990-1991), respectively. Hax7ing in mind the abundance of offsprinq, we consider that the assessments made by LCOHOR analysis reflect more correctly the actual state of whiting stocks during the last 4 years. The sharp decrease of the whiting bio-

due to the low abundant year-classes from 1987 t o 1989. The increase whiting biomass after 1991 is conditioned by the strong year-class 1990

-

^more^than⁵⁰^and⁷ times in comparison with year- classes 1987 and 1988, respectively.

Arkhipov and Rovnina's (1990) data confirm the considerable decrease in abundance of the offspring after 1987, which to show that the natural reproduction the whiting was seriously disturbed between 1987-1989.The reasons for that are complex and are related to the sig- nificant alterations of the environment-the the phytoplan- cton was more frequent and more extensive,leading to considerable pla- gue of benthonic and dimersal fishes and invertebrate fauna (Moncheva, Petrova-Karadjova, Palasov,1993 1 . The food supply the larvae and

young fish was also subjected to rapid variations connected with.the overall changes of the environment as well as with the mass develop- ment of the new ctenophore Mnemia mccradyi

73

CIHEAM - Options Mediterraneennes

(3)

which appears to vigorous competitor in ralation to the small-size crustaceans from Copepoda and also presents itself as a predator eggs and fish larvae (Zaika,Sergeeva,lP90).

Table

Initial (calculated by 1 and mean biomasses (calculated by whiting along ..qarian Black sea c o a s t (1976-1993)

r ^I ¹

IYears I ""Bio-let * " F l o - l e t I i1976

i

^27273.6

i

^0.0628

i

^I ^I

I 1 1 - 1 12652.2 I , O . 0997 I 11977 I 25281.6 I 0.0797 I I I I l1978 I 25234.4 I 0.1219 I I

I 1 - 1 16072.3 I 0.1161 I

11979 I 25104.2 I 0.11S7 I I I I

11980 I 21610.6 I 0.2451 I I I

I 1 - 1 12441.1 I 0.1946 I

11981 I 17861.1 I 0.2284 I I

I

1 I I

11982 l 15693.3 1 0.2703 I I I

I 1-1 10415.6 0.1945 I

11983 I 13469.7 I 0.1545 I I I

I

I 1 1 I

1 I

1

i 1 9 8 4

i

^14687.6

i

^0.1497

i

I I

I 1 - 1 10568.9 I 0.1557 I

11985 I 14632.4 I 0.1324 I I l I (198b I 13967.5 I 0.1137 I I

I 1 - 1 6886.1 I 0.1511 1

11987 I 12760.9 0.1314 I

I

I ,

I l

1 1

i

¹⁹⁸⁸

i

^10893.4

i

^0.1230

i

^I ^I

11989 I 12100.6 I 0.0765 I l I

I 1 - 1 6343.2 I 0.1245 I

i1990

i

^14543.4

i

^0.0253

i

I 1 - 1 2554.1

11991 15399.6 I 0.0206 1 l 11992 I 15123.8 I 0.0427 I

1 4 - 1 6397.7

l1993 I I 0.0657

I I I

0.1113 I I I 0.0690

i

I I

1 t o 4+

10-18+ cm

4

1 to 4 +

classes 18+

(4)

REFERENCES

ARKHIPOV.A.G., ROVNINA 1 9 9 0 . Coll.papers Vses.Nauchno-Issled.

DASKALOV 1 9 9 3 . D.E.A., Univ., Aix-Marceille, (in French)

DOMASHENKO G.P., SEROBABA I.I., 1 9 9 0 . Coll. papers of Vses. Nauchno-

142-145 (in Russian)

IVANOV L.S., 1 9 8 3 . Proc.Inst.Fish., Varna, X X , 7-46 (in Bulgarian) IVANOV 1 9 8 9 . Hydrobiology,Sofia, v . 3 4 , 6 8 - 8 9 (in Bulgarian)

64-80 (in Russian)

KONSULOFF A . , KONSULOVA Ts., 1 9 9 3 . NATIONAL BIOLOGICAL RESOURCES CON- SERVATION STRATEGY, 473-514 (in Bulgarian with coppy English)

MESNIL 1 9 8 9 . ANACO: Software, FAO, Rome

MONCHEVA S.P., PETROVA-KARADJOVA V., PALASOV A., 1 9 9 3 . Proceedings of 6th Conference on Toxic Marine

PRODANOV K.? 1 9 8 4 . Ph.D. dissertation (in Bulgarian) SPARRE P., 1 9 8 7 . LCOHOR: Software, FAO, Rome

Zaika V.E.,SERGEEVA Russian)

75