Leg 4b, Cadeia Fernando De Noronha (08.02.95 -14.02.95)

R.V "Victor Hensen" left Natal harbour in the morning (9:00) of the 8th of February towards Fernand o de Noronha. I n the mornin g o f th e 9t h o f February , "Victo r Hensen " arrive d i n the operatio n are a close to Fernando de Noronha and regular station work was started at 06:00 am.

Following the cruise plan, 29 stations (including 7 stations with CTD-profiles only, ref. to attached list of stations STAT02 and Fig.4) were visited around the seamounts and banks in the area of Fernand o de Noronha. "Victor Hensen" left this operation area at noon of the 14th of February for Natal and ar-rived in the morning of the 15th of February.

In Situ measurements and sampling procedures were executed in accordance to those described for leg 4a.

Physical Oceanography

P. Travassos (UFRPE) & T.Vaske (UFRPE )

Temperature, salinit y an d oxyge n profile s wer e obtaine d i n paralle l wit h wate r sample s a t eac h station using a CTD aiming to detect the hydrological structure around the oceanic islands and over seamounts, maximum launching depth was 400m.

Primary Production, Pico,- Nano- and Microplankton T. Rodrigues Jr. (UFRPE) & G. Melo (UFPB)

The water samples for primary productivity, chlorophyll, nutrients, dissolved oxygen and fractionated plankton (pico, nano and microplankton) were taken in approriate depth ranges indicated by "Secchi-depth" and fluorescence measurements .

Simulated i n sit u experiment s measurin g gross-oxygen-productio n wer e performe d o n eac h firs t station of the day (S-001 , S-019 , S-035, S-045 , S-052 an d S-057) an d the incubatio n perio d of th e

Tab.2: List of stations, Fernando de Noronha leg 4b 08.02.-14.02.95

Hydrography an d Niskin bottles Fluorescence prob e Apstein net Current mete r Van-Veen sample r

equipment lauche d

SD,CTD,FL,AN,BO,NN

samples was 6 hours. Samples for chlorophyll analyses were taken for all stations with CTD-coupled casts. Pico-, nano-, and microplankton were collected at 2 stations every day. Samples for nutrient s were obtained for all stations with CTD casts and frozen for future analyses.

VAN-VEEN-Sampler A. C. Beltrao (UFPE )

Whenever th e statio n dept h ove r seamount s wa s appropriat e (<250m , S003755m , S036/55m , S -038780m, E-046/70m and S-048/63m),two benthos and sediment samples were collected by using a VAN-VEEN type sampler. At station S-056/237m sampling failed. Benthos were treated by passsing the samples through 250|im and 500u.m sieves. Finally, the material was fixed in 10 % formalin. The collected sediment was stored in plastic bags for further analyses.

Ichthyoplankton, Macrozoo- and Megaplankton Ichthyoplankton, Biochemistry and Histology B. Ueberschar (IfMK ) & V. Vieira (IFRPE)

Fish larva e fo r nutritiona l conditio n (b y mean s of enzym e analysi s an d histology ) an d growt h rate s were selecte d from al l 100 m BONGO-hauls. Immediatel y afte r takin g the BONGO-haul , samples of both net s (300u. m and 500nm) wer e sorte d for fish larvae . The larva e were kep t o n ic e to preven t

52

37 36 34 33

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37 « !

. FERNAND O DE NORONHA

O i

BRAZIL

6 37 36 34 ^"lial"i|iM""im!i""mi"'

33 ₃₂

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Fig. 4: The stations visited, their numbers and their locations for leg 4b is given.

autolysis, transferred int o Eppendorf-cap s (biochemistry ) o r glass vials (histology ) an d immediatel y after finishin g th e sortin g procedur e sample s wer e store d i n a specia l deep-freeze r (-74°C) . Fo r biochemical analysis , abou t 68 0 larva e o f abou t 3 0 tax a wer e collecte d o n 2 2 stations . Fo r histological analysi s abou t 52 0 larva e wer e preserve d i n phosphate-buffere d formali n o r i n Glutardialdehyd.

Fig.5 show s abundanc e an d distributio n fo r fis h larva e sorte d fro m th e 100 m BONGO-hau l fo r biochemistry an d histology . Highes t larva l abundanc e wa s locate d t o the western mos t par t o f th e grid. This will be related to condition analyses an d to supplementing dat a (e.g. hydrography, primar y production, mikrozooplankton). A high number o f eel-lik e larva e (Leptocephalu s larvae ) were foun d at some stations compared to the usual very low densities of eel-like larvae in oceanic samples. This could indicate favourable nutritiona l conditions for this type of larva e which are supposed to be able to assimilate dissolved organic matter (DOM, free amino acids).

When cephalopod larva e were detecte d i n the samples , they wer e treated i n the sam e manne r a s fish larva e bu t froze n seperatel y fo r late r identificatio n an d conditio n analysi s (U.Piatkowski , IfM K and M. Haimovici, FURG). In total, 27 cephalopod larvae from 12 stations stations were preserved.

Abundance and distribution of tuna and other fish larvae

A. Ropke (NOAA), R.Lessa (UFRPE) , P.Mafalda (UFRPE) , C.Ebel (IfMK )

Between th e 9t h an d th e 14t h o f Februar y 1995 , 2 2 station s wer e sample d aroun d th e Islan d o f Fernando de Noronha, Atol das Rocas and the adjacent seamounts and on the Sirius and the Guara Bank.

3 7 3 6 35 3 4

:.iiiiiiaia •.'.:: :^•:'.:•••};l^:^^•;::h^:••:^:

M^^••• ,:-V::-.

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^ 3

Q 0 Larvae/Haul A 12 0 Larvae/Halul

HlBi|nii|BlMnii nimimtBiapiuluunuiBMii IIJI um|immuini|uu|uiniiiua

34 33

Fig. 5: Abundance and density of ichthyoplankton sampled from the 100m BONGO-haul (both nets) for biochemical analyses and histology (larval performance) related to the stations visited on leg 4b is shown.

A black circle indicates 120 fish larvae/haul, hollow circles indicate zero larvae/haul. Stations with CTD casts only are noted

These areas are important fishing grounds for the tuna fishery of North-eastern Brazil. On the Sirius and Guara Bank intensive fishing activities of longliners could be observed during stationwork.

Sampling wa s done usin g a BONGO-ne t equipe d wit h 300u m and 500u.m nets. On every station , double oblique hauls were made down to a depth of 150 m, 100 m and 50m respectively. On this leg a total of 124 plankton samples were obtained.

59 sample s have bee n sorte d fo r Scombrid i. e tuna larva e yieldin g 9 identifie d tun a larva e an d 6 larvae which showed meristi c caracteristics of tuna larvae. These larvae will need further verificatio n and identification in detail in the laboratory in Miami (A. Rbpke , RSMAS).

Differences of the total numbe r of caught larva e could be observed betwee n samples taken at full daylight an d samples take n durin g dus k an d in the evening. I t mus t b e considered tha t th e give n sampling desig n (i.e . sampling durin g daylight ) coul d underestimat e th e "real " abundanc e o f fish -larvae significantly.

The ichthyoplankto n communit y o f the sampled area s reveale d typica l oceanic characteristic s wit h dominating taxa of Myctophidae, Photichthyidae and Gonostomatidae.

54

Other groups present in the samples were:

Anguilliformes (several types of Leptocephali ) Ophidiiformes

Bothidae

Bregmacerotidae: Bregmaceros spp. (8. atlanticus) Carangidae

Coryphaenidae Dactylopteridae Exocoetidae Gobiidae Hemiramphidae Labridae Serranidae Trichiuridae

The 9 identifie d tun a larva e an d th e 6 questionabl e larva e wer e store d i n 95 % ETO H fo r furthe r analysis.

Macrozoo- and Megaplankton

K.Valenca Correia (UFPE) & J.Lins de Oliveira (UFRN)

Macrozoo- and Megaplankton obtaine d usin g NEUSTO N ne t at al l stations an d from BONGO-hauls from 150m , 100 m and 50m will be analyse d b y Keni a Valenca Correia , Depto . Zoologia, UFPE , as described i n the first sectio n of thi s repor t (2.3.3.3) . Lobste r larva e collected by BONGO-ne t wil l b e analysed by Jorge Lins de Oliveira, Depto. Oceanografia, UFRN.