Inshore trawl survey of the west coast of the South Island and Tasman and Golden Bays, March April 2007 (KAH0704)

Transcription

1 New Zealand Fisheries Assessment Report 7/41 November 7 ISSN Inshore trawl survey of the west coast of the South Island and Tasman and Golden Bays, March April 7 (KAH0704) M. L. Stevenson

2 Inshore trawl survey of the west coast of the South Island and Tasman and Golden Bays, March-April 7 (KAH0704) M. L. Stevenson NIWA POBox 893 Nelson New Zealand Fisheries Assessment Report 7/41 November 7

3 Published by Ministry of Fisheries Wellington 7 ISSN Ministry of Fisheries 7 Citation: Stevenson, M.L. (7). Inshore trawl survey of the west coast of the South Island and Tasman and Golden Bays, March-April 7 (KAH0704). New Zealand Fisheries Assessment Report p. This series continues the informal New Zealand Fisheries Assessment Research Document series which ceased at the end of 1999.

4 EXECUTIVE SUMMARY Stevenson, M.L. (7). Inshore trawl survey of the west coast of the South Island and Tasman and Golden Bays. March-April 7 (KAH0704). New Zealand Fisheries Assessment Report p. This report gives the results of the eighth in a series of inshore trawl surveys along the west coast of the South Island from Farewell Spit to the Haast River mouth and within Tasman and Golden Bays at depths from 0 to m by RV Kaharoa. The survey took place in March-April 7. It used a two-phase design optimised for giant stargazer, red cod, red gumard, spiny dogfish, and tarakihi. Biomass estimates, catch distribution, and population length frequencies for the major species are described. The biomass estimates and coefficient of variation (c.v.) for the target species were giant stargazer, 1603 t (1%); red gumard, 553 t (17%); red cod, 1638 t (19%); spiny dogfish, 691 t (14%); and tarakihi, 1189 t (1 %). Target c.v.s were 0-5% for red cod and 0% for the other species. Other commercial species with c.v.s less than 0% were barracouta, gemfish, sea perch, and arrow squid. The estimates of total biomass for giant stargazer, red gumard, and spiny dogfish were higher than for the previous survey in 5 and for giant stargazer were the highest for any survey in the series. A total of 11 school shark, 31 rig, 56 rough skate, and 7 smooth skate were tagged during the survey. In addition, 773 tarakihi were tagged during two days at the end of the survey which were reserved for tagging juvenile tarakihi in Tasman Bay to clarify stock affiliations. 3

5 1. INTRODUCTION This report presents results from the eighth in a time series of stratified random trawl surveys using RV Kaharoa in waters between 0 and m deep off the west coast of the South Island, and within Tasman and Golden Bays. The survey was optimised for giant stargazer (Kathetostoma spp.), red cod (Pseudophycis bachus), red gumard (Chelidonichthys kumu), spiny dogfish (Squalus acanthias), and tarakihi (Nemadactylus macropterus). The results of earlier surveys in this series were reported by Drummond & Stevenson (1995a, 1995b, 1996) and Stevenson (1998,, 4). The series was reviewed by Stevenson & Hanchet (0) and species to be included in future reports were reviewed by Stevenson and Hanchet (7) The principal objective of the surveys is to develop a time series of relative abundance indices for giant stargazer, red cod, red gumard, spiny dogfish, and tarakihi for the inshore waters of the west coast of the South Island and within Tasman and Golden Bays. Changes in the relative abundance and length frequency distributions over time should reflect changes in the abundance and size distributions of the underlying fish populations. A standardised index of relative abundance estimates for key inshore species will therefore provide the basis for stock assessment and management strategies. This is particularly important for giant stargazer (STA 7) and rig (SPO 7) which are currently in the Adaptive Management Programme (AMP) (Ministry of Fisheries 7). This report details the survey design and methods, and provides relevant stock assessment data for commercially important Individual Transferable Quota (ITQ) and non-itq species. 1.1 Programme objective To determine the relative abundance and distribution of inshore finfish species off the west coast of the South Island, and Tasman Bay and Golden Bay; focusing on red cod (Pseudophycis bachus), red gumard (Chelidonichthys kumu), stargazer (Kathetostoma giganteum), tarakihi (Nemadactylus macropterus), and spiny dogfish (Squalus acanthias). Specific objectives (7). To determine the relative abundance and distribution of red cod, red gumard, spiny dogfish, giant stargazer, and tarakihi off the west coast of the South Island from Farewell Spit to the Haast River mouth, and within Tasman Bay and Golden Bay by carrying out a trawl survey. The target coefficients of variation (c.v.s) of the biomass estimates for these species are as follows: red cod (0-5%), red gumard (0%), giant stargazer (0%), tarakihi (0%) and spiny dogfish (0%). 3. To collect the data and determine the length frequency, length-weight relationship and reproductive condition of red cod, red gumard, giant stargazer, tarakihi, and spiny dogfish. 4. To collect otoliths from red cod, red gumard, giant stargazer, and tarakihi, and spines from spiny dogfish. 5. To collect the data to determine the length frequencies and catch weight of all other Quota Management System (QMS) species. 6. To tag live skate, school shark, and rig. 7. To determine stock affiliation of pre-recruit tarakihi in Tasman/Golden Bay nursery area using mark recapture. 4

6 8. To identify benthic macro-invertebrates collected during the trawl survey. 9. To review data collected by the WCSI series to determine for which species relative abundance trends and size composition information should be provided in each survey report. 1.3 Timetable and personnel RV Kaharoa departed Wellington on March 7 and trawling started on 3 March. Kaharoa berthed in Westport on 4 April to unload fish, pick up supplies, and change science staff. Trawling finished on 1 April and Kaharoa returned to Nelson to pick up supplies for the tarakihi tagging and change science staff. Additional MFish staff joined the vessel on 15 and 16 April to assist with the tagging work. Tagging commenced on 15 April and concluded on 16 April. The vessel returned to Nelson on 17 April where science staff disembarked. Kaharoa remained in Nelson for maintenance Michael Stevenson was project and voyage leader and was responsible for final database editing. The skipper was Michael Baker.. METHODS.1 Survey area and design The survey area (Figures 1 a and b) covered depths of 0- m off the west coast of the South Island from Cape Farewell to Karamea; 5- m from Karamea to the Haast River mouth; and within Tasman and Golden Bays inside a line drawn between Farewell Spit and Stephens Island. The maximum depth on the west coast north of Karamea was limited to m because of historically low catch rates in the - m range. The survey area of km, including untrawlable ground, was divided into 16 strata by area and depth (Table 1, Figures 1a and b). Strata were identical to those used in previous surveys. The trawlable ground within the survey area represented 84% ofthe total survey area. Phase 1 station allocation was optimised to achieve the target c.v.s using the R program allocate. Stratum area and catch rate data from previous Kaharoa trawl surveys were used to simulate optimal allocation and simulations were run for each target species separately. Results indicated that 68 stations and a two-phase design (after Francis 1984) were required to achieve the predicted c.v.s with about 80% of stations allocated to phase 1. Results also showed that gumard and red cod required the most effort to achieve the target predicted c.v.s, with 55 and 59 stations required, respectively. The proposed phase 1 survey design of 68 stations was based on the maximum number of stations required for each species in each stratum. Before the survey began, sufficient trawl stations to cover both first and second phase stations were randomly generated for each stratum by the computer programme 'Rand_stn v.1' (Vignaux 1994). The stations were required to be a minimum of 5.6 km (3 n. miles) apart. Non-trawlable ground was identified before the voyage from data collected during previous trawl surveys in the area and excluded from the station allocation program. The distribution of non-trawl able ground is given in Table 1 and shown in Figures 1a and lb. 5

7 . Vessel, gear, and trawling procedure RV Kaharoa is a 8 m stem trawler with a beam of 8. m, displacement of 30 t, engine power of 5 kw, capable of trawling to depths of 500 ill. The two-panel trawl net used during the survey was designed and constructed in 1991 specifically for South Island inshore trawl surveys and is based on an 'Alfredo' design. The net was fitted with a 60 mm (inside measurement) knotless codend. Details of the net design were given by Drummond & Stevenson (1995a). Gear specifications were the same as for previous surveys (Drummond & Stevenson 1996). Doorspread and headline height measurements were recorded from Scanmar monitoring equipment and an average taken of five readings at min intervals during each tow. When no direct readout was possible, doorspread value was calculated as being equal to the mean of the doorspread from stations within the same stratum depth range for which direct readings were available. A Seabird conductivity, temperature, and depth (CTD) sensor was used to record sea temperatures, conductivity, and water pressure. A Mac Marine Bottom Contact Sensor (BCS) was mounted at the centre of the groundrope and used to determine net contact with the sea floor. If the graphic output (see Stevenson & Hanchet (6) for examples) showed the net had not maintained good bottom contact, it was reviewed and a determination made on the suitability of the tow for inclusion in estimating biomass. Procedures followed those recommended by Stevenson & Hanchet (1999). All tows were undertaken in daylight, and four to six tows a day were planned. For each tow the vessel steamed to the station position and, if necessary, the bottom was checked with the depth sounder. Once the station was considered trawlable, the gear was set away so that the midpoint of the tow would coincide as nearly as possible with the station position. The direction of the tow was influenced by a combination of factors including weather conditions, tides, bottom contours, and the location of the next tow but was usually in the direction of the next tow. If the station was found to be in an area of foul or the depth was out of the stratum range, an area within 5 km of the station was searched for a replacement. If the search was unsuccessful, the station was abandoned and the next alternative from the random station list was chosen. Standard tows were of 1 h duration at a speed over the ground of 3 kn and the distance covered was measured by GPS. The tow was deemed to have started when the net monitor indicated the net was on the bottom, and was completed when hauling began. A warp length of m was used for all tows at less than 70 m depth (10-.8). At greater depths, the warp to depth ratio decreased linearly to about.4: 1 at ill..3 Water temperatures The surface and bottom temperatures at each station were recorded by the CTD unit. Surface temperatures were taken at a depth of 5 m and bottom temperatures when the net settled on the bottom. Bottom temperatures were taken at about 5 m above the sea floor because the CTD rests on the net just behind the headline..4 Elasmobranch tagging As soon as the net was brought on board, lively ng (Mustelus lenticulatus), school shark (Galeorhinus galeus), and rough (Dipturus nasutus) and smooth (D. innominatus) skate were separated from the catch and tagged with a single Hallprint dart tag. Sharks were tagged in the dorsal 6

8 muscle at the rear of the dorsal fin and skates were tagged near the centre of the left wing. Length, weight, and sex were recorded for each tagged fish and the fish immediately returned to the water..5 Catch and biological sampling The catch from each tow was sorted into species on deck and weighed on kg electronic motioncompensating Seaway scales to the nearest 0.1 kg. Finfish, squid, and crustaceans (scampi) were classified by species: crabs, shellfish, and other invertebrate species not readily identified were frozen for later identification because of difficulty in identifying individual species and the limited sorting time available between tows. Unidentified specimens were placed in sealed plastic bags with a label noting the trip code and station number. Length, to the nearest whole centimetre below the actual length, and sex (where possible) were recorded for all ITQ species, either for the whole catch or a randomly selected subsample of up to fish per tow. Individual fish weights were collected for the target species, rig, rough skate, smooth skate, and school shark and reproductive state for the target species. Individual fish weights were measured to enable length-weight relationships to be determined for scaling length frequency data and calculation of biomass for length intervals. Samples were selected non-randomly from the random length frequency sample to ensure a wide range was obtained for each species. Up to five otolith pairs per sex per centimetre size class were collected from length frequency samples for giant stargazer, red cod, red gurnard, spiny dogfish, and tarakihi. Similarly, up to five second dorsal spines per sex per centimetre size class were collected from spiny dogfish..6 Data analysis Relative biomass estimates and scaled length-frequency distributions were estimated by the area-swept method (Francis 1981, 1989) using the TrawlSurvey Analysis Program (Vignaux 1994). All data were entered into the Ministry of Fisheries trawl database. The following assumptions were made for estimating biomass with the TrawlSurvey Analysis Programme. 1. The area swept during each tow equalled the distance between the doors multiplied by the distance towed.. Vulnerability was 1.0. This assumes that all fish in the area swept were caught and there was no escapement. 3. Vertical availability was 1.0. This assumes that all fish in the water column were below the headline height and available to the net. 4. Areal availability was 1.0. This assumes that the fishstock being sampled was entirely within the survey area at the time of the survey. 5. Within the survey area, fish were evenly distributed over both trawl able and non-trawl able ground. Although these assumptions are unlikely to be correct, their adoption provides the basis for a time series of relative biomass estimates (Stevenson & Hanchet 1999). All assumptions listed are consistent with those used for previous surveys in the series. All stations where the gear performance code was 1 or (all 69 stations) were used for biomass estimation. The c.v. associated with estimates of biomass was calculated by the method of Vignaux (1994). 7

9 Length frequencies were scaled by the percentage of catch sampled, area swept, and stratum area. The geometric mean functional relationship was used to calculate the length-weight coefficients for species where sufficient length-weight data were collected on this survey. For other species, coefficients were chosen from the trawl database and a selection was made on the basis of whether coefficients were available from previous surveys in the series or on the best match between the size range of the fish used to calculate the coefficients and the sample size range from this survey (Appendix 1). Sex ratios were calculated using scaled population numbers and are expressed as the ratio of males to females..7 Tarakihi tagging At the end of the standard survey, the vessel returned to Tasman Bay where the greatest number of small tarakihi were caught during the regular survey (station 19). The CTD and BCS were not deployed for this portion of the project. Tow duration was reduced to 10 minutes and at the end of the tow the codend was immediately lowered into an aerated tank to minimise the time fish spent out of the water. Usually, tagging began after the tarakihi were sorted from the rest of the catch and placed in a second aerated tank. However, for three large catches of tarakihi, tagging began immediately without sorting. Tagged fish were released before travelling to the next station. 3. RESULTS Results are presented slightly differently in this report compared to those from previous surveys in accordance with a recent review to determine for which species relative abundance trends and size composition information should be provided in each survey report (Stevenson & Hanchet, 7). Biomass estimates and c.v. s by stratum and catch rates by stratum are given for the 0 most abundant commercially important species. Trends in biomass and comparative length frequency distributions are presented for the target species and for those species for which it is thought the surveys could be monitoring adults and/or pre-recruit abundance. Length frequency distributions for other species are given for this survey only if the species is one of the 0 most abundant commercially important species. Catch rate figures are given only for the target species. 3.1 Survey area, design, and gear performance Trawling began in Tasman and Golden Bays and after 4 days working continued on the west coast in a generally north to south direction. Two days were lost to bad weather, two days were lost because of equipment problems, and one day was used unloading fish. Sixty-nine stations were successfully completed, 67 in phase 1 and in phase. Station density ranged from one station per 10 km in stratum 17 to one station per 1078 km in stratum, with an average density of one station per 371 km (Table 1). At least three stations were completed in all 16 strata and all project and survey objectives were achieved. The survey area, with stratum boundaries and station positions, is shown in Figures 1 a and 1 b and individual station data are given in Appendix. The two phase stations in stratum 1 were allocated to reduce the tarakihi c.v. towards the target levels. Catch rates of the remaining target species were not used for allocation of phase stations because the c.v.s for these species were within target levels. 8

10 Tow and gear parameters by depth are shown in Table. Doorspread varied from 67.5 to 91.5 m and headline height varied between 4.1 and 5.7 m (Table, Appendix ). Measurements of headline height and doorspread, together with BCS output and observations that the doors and trawl gear were polishing well, indicated that the gear was, in general, operating correctly. Gear parameters were similar to those of previous surveys, indicating consistency between surveys (Stevenson & Hanchet 0). 3. Catch composition A total of about 39. t of fish was caught from the 69 biomass tows at an average of 568 kg per tow (range kg). Amongst the chordate fish catch, 1 agnathan, 19 species of elasmobranchs, and 65 teleost species were recorded. Species codes, common names, scientific names, and catch weights of all species identified during the survey are given in Appendix 3. The most abundant species by weight was spiny dogfish with 8.4 t caught (1.4% of the total catch). The top four species, spiny dogfish, barracouta, red cod, and two-saddle rattail made up 45% of the total. Giant stargazer, red cod, red gurnard, and tarakihi made up 6., 7.6,.3, and 4.4% of the catch, respectively. Arrow squid, barracouta, spiny dogfish, and scaly gurnard occurred in over 80% of the tows (see Appendix 3). Eighty-two species of invertebrates were identified from retained specimens (Appendix 4). This compares to 40 species in 5,45 species in 3, and over 150 in 0. However, the numbers of invertebrate species does not necessarily indicate the level of abundance or biodiversity in the survey area because the gear is not designed to collect benthic macroinvertebrates. In addition, station location strongly influences the incidence of some groups (e.g., bryozoans). 3.3 Catch rates and species distribution Distribution by stratum and catch rates for the target species are shown in Figures a-e (biomass tows only). Catch rates are given in kilograms per square kilometre. On average, a standard tow covers 0.44 km, therefore a catch rate of kg.km-, equates to a catch of 44 kg. Mean catch rates for the 0 most abundant commercially important species by stratum are given in Table Biomass estimation Relative biomass estimates for all ITQ species are given in Table 4. Spiny dogfish had the largest estimated biomass followed by barracouta, dark ghost shark, red cod, and giant stargazer. Biomass and c.v.s for the target species were: giant stargazer, 1603 t (1%); red gurnard, 553 t (17%); red cod, 1638 t (19%); spiny dogfish, 691 t (14%); and tarakihi, 1189 t (1 %) (Table 4). Biomass estimates of recruited fish for barracouta, blue warehou, giant stargazer, hoki, John dory, red cod, red gurnard, rig, sand flounder, school shark, silver warehou, and tarakihi are given in Table 5. For the target species, giant stargazer, red cod, red gurnard, and tarakihi, the percentages of total biomass that were recruited fish were 98%, 47%, 78%, and over 89% respectively. Biomass estimates by year class (where discernible from the length frequency distributions) for barracouta, blue warehou, hake, hoki, jack mackerel, red cod, red gumard, school shark, silver warehou, and tarakihi are given in Table 6. For red cod, the 1 + cohort made up about 48% of the total 9

11 biomass. For red gumard, the + cohort made up 3% of the total biomass, and for tarakihi the + cohort made up 11 % of the total (Table 6). The relative biomass estimates and c.v.s for the 0 most abundant commercially important species are given by stratum in Table 7. Survey time series trends in biomass for the target species and for those species where the surveys are likely to be monitoring adult and/or pre-recruit abundance are shown in Figure Water temperatures Isotherms estimated from CTD surface and bottom temperature recordings are shown in Figures 4 and 5 respectively. Temperatures can not be directly compared to surveys before 5 because earlier data were not taken from calibrated recordings. Both surface and bottom temperatures were generally lower than in Length frequency and biological data The numbers of length frequency and biological samples taken during the survey are given in Table S. Comparative scaled length frequency distributions for the target species and for the eight other species the surveys may be monitoring are shown in Figures 6a-m in alphabetical order by common name. Scaled length frequency distributions from this survey for other commercial species where more than fish were measured are shown in Figure 7 in alphabetical order by common name. Length-weight coefficients were determined for giant stargazer, red cod, red gumard, spiny dogfish, tarakihi, rig, rough skate, and school shark from data collected on this survey (Appendix 1). Details of gonad stages for giant stargazer, red cod, red gumard, and tarakihi are given in Table Elasmobranch tagging A total of 11 school shark was tagged (5 females and 60 males) ranging in length from 37 cm to 141 cm. In addition, 31 rig (10 females, 1 males), 56 rough skate (34 females, males), and 7 smooth skate (4 females, 3 males) were tagged. 3.8 Tarakihi tagging The juvenile tarakihi tagging was very successful with the use of two aerated holding tanks providing good survival. Locating a concentration of juveniles during the regular survey enabled maximum use of the time available. Most tarakihi did not require venting even when trawled from a depth of 50 m. A total of 773 tarakihi ranging from 10 to 34 cm fork length were tagged over two days at the end of the regular survey. This is at the upper end of the estimate (50-S00) of the number of fish that would be tagged. Two fish were known to not survive (one was eaten by a mollymawk on release) but most swam away vigorously. 10

12 3.9 Target species Giant stargazer Giant stargazer were caught at 77% of all stations with the highest catch rates south of Cape Foulwind in depths of - m (strata 8, 1, and 15) (Figure a, Table 3). The total estimated biomass of 1630 t was the highest in the series. Ninety-two percent of the relative biomass estimate was south of Cape Foulwind, and 79% (188 t) was within the - m depth range (Table 7). There were more fish less than 45 cm caught on this survey than in previous years (Figure 6d), but no clear year class modes were apparent in the length frequency distribution. The sex ratio (male:female) of 1.6:1 overall was the highest of the series (see Figure 6d). The low numbers oflarge females (over 70 cm) continues the pattern first noted in 0. Virtually all females under 50 cm total length were immature or had resting gonads, but above this size, most had maturing gonads. Most males under 40 cm were immature or resting, and most males over 40 cm were maturing (Table 9) Red cod Red cod were caught at over 75% of all stations, with the highest catch rates in strata 7, 11, 14, and 16 (Figure b, Table 3). Over 80% of the total biomass was south of Cape Foulwind and 94% (1545 t) was from depths less than m (Table 7). The length frequency data show a dominant 1+ cohort (4-38 cm) present at the time of the survey. Only a few fish in the 10-0 cm range were caught which would represent 0+ fish. However, this mode is slightly stronger than in 3 and 5 (Figure 6h). The sex ratio (male:female) of 1.1:1 was the most even of any of the surveys (see Figure 6h). Most red cod examined had immature or resting gonads, and a few fish were at later stages of reproductive development (Table 9) Red gurnard Red gurnard were caught at all stations in Tasman and Golden Bay and at all but one station in depths less than m along the west coast (Figure c). The highest catch rates were in strata 7 and 19 (Table 3). The relative biomass estimate of 553 t was higher than the previous two surveys (Table 4, Figure 3). There was a substantial difference in the length frequency distributions between this survey and 3 and 5 with considerably higher numbers of pre-recruit fish caught in 7 (Figure 6i). The recruited biomass estimate (30 cm or over) was 43 t (78% of the total) with 189 t occurring on the west coast (Table 5). Almost 99% of red gurnard biomass was at depths less than m and no gurnard were caught deeper than m (Table 7). The overall sex ratio (male:female) was 1.6: 1 which was the highest for any survey in the series (see Figure 6i). Most red gurnard over 30 cm had developing or mature gonads (Table 9) Spiny dogfish Spiny dogfish were caught at over 88% of all stations with the highest catch rates in strata 15, 11, and 1 (Table 3, Figure d). The relative biomass estimate of 6175 t was similar to that of 5 (Table 4, Figure 3). There were considerably fewer fish less than 50 cm caught on this survey than from previous surveys where spiny dogfish were measured (Figure 61). Over 99% of the estimated biomass was at depths less than m (Table 7). The sex ratio of (male:female) 0.87:1 was similar to the previous two surveys but lower than in 1997 and 0 (see Figure 61). 11

13 3.9.5 Tarakihi Tarakihi were caught at 68% of stations with the highest catch rates in strata 1, and 15 (Table 3, Figure e). Almost 89% of the biomass estimate was recruited fish (5 cm and over) (Tables 4 and 5). The length frequency data exhibit a strong mode at 17-3 cm of+ fish. There is a weak mode at cm of 0+ fish and a few fish at 6-9 cm, probably 3+ fish (Figure 6m). These are the strongest pre-recruit modes since Of the total tarakihi biomass (1189 t), over 89% was on the west coast, and over 6% (744 t) of this was at depths between to m (Table 7). The sex ratio for the estimated population was 0.87:1 (see Figure 6m). There was little reproductive development in tarakihi under 30 cm FL, but for bigger fish the full range of gonad stages was recorded (Table 9) Other species Barracouta Barracouta were caught at over 84% of all stations and represented 8.4% of the total catch (Appendix 3). The highest catch rates were in strata 1 and 19 (Table 3). Over 9% of the total biomass estimate was recruited fish (50 cm and over) (Tables 4 and 5) and the length frequency distribution was similar to that in 5 except for a mode at 5-15 cm which was stronger than for any previous survey (Figure 6a). Blue warehou Blue warehou were caught at 33% of all biomass stations with the highest catch rates in stratum 15 (Table 3). Less than 55% of the total biomass was recruited fish (54 cm or over) (Tables 4 and 5). The length frequency distribution shows three pre-recruit modes at 10-3 cm, 3-30 cm, and cm. The mode at cm is the most evident this year class (+) has been in any survey in the series (Figure 6b). Gemfish Gemfish were caught at only 10 stations and in low numbers (Appendix 3, Table 8). The strong mode present in 3 and 5 is no longer apparent in the length frequency distribution (Figure 6c). Jack mackerel (Trachurus declivis) Trachurus declivis was caught at 9 stations but in low numbers (Appendix 3, Table 8). The biomass estimate of 6 t was the lowest of any survey in the series (Table 4). The length frequency distribution is similar to those from 3 and 5, with few small fish and a weak adult mode (Figure 6e). John dory John dory were caught at 1 biomass stations with the highest catch rates in stratum 19 (Table 3, Appendix 3). The biomass estimate of 171 t is lower than 3 and 5 but higher than for any other survey (Table 4). The length frequency distribution shows few small fish but good numbers of large females (Figure 6f). 1

14 Ling Ling were caught at just over half of all stations with the highest catch rates in stratum 16 (Appendix 3, Table 3). Although the biomass estimate is lower than for 5, the estimated population is higher because of greater numbers of fish less than 70 cm total length, especially males (Figure 6g). Rig Rig were caught at just over half of the stations, with the highest catch rates in strata 7 and 8 (Appendix 3, Table 3). The estimated biomass of383 t is the highest in the series except for 1995, but the c.v. was the highest in the series (Table 4, Figure 3). The length frequency distribution shows good numbers of fish less than cm total length but few fish over that size (Figure 6j). School shark School shark were caught at about 74% of all biomass stations with the highest catch rates in strata 1 and 15 (Appendix 3, Table 3). The estimated biomass of 816 t was higher than in 3 and 5 but still lower than all earlier surveys (Table 4, Figure 3). The length frequency distribution shows a reasonably strong mode at cm compared to previous surveys, but there were few fish caught greater than 110 cm (Figure 6k) Invertebrates The amount and diversity of invertebrates was greater than in 3 and 5 but less than in 0 (Stevenson, 4, 6). There were no rare or invasive species identified (Appendix 4). 4. DISCUSSION Following the recommendations of a review of the previous seven surveys in the series (Stevenson & Hanchet, 7), results in this report include information on species where it is thought the surveys may be monitoring adult or pre-recruit abundance. The 7 survey was the eighth the March-April Kaharoa time series for the west coast of the South Island and Tasman and Golden Bays, the first of which was in 199. Sixty-nine biomass stations and 17 tarakihi tagging tows were successfully completed. The mean catch per station of 567 kg is similar to that in 5 (597 kg), but less than the first four surveys in the series. The c.v.s associated with the biomass estimates for the target species were all lower than or very close to the target c.v.s. Other commercial species with c.v.s of 0% or less were arrow squid (9%), barracouta (14%), gemfish (19%), school shark (0%), and silver warehou (0%). As in all previous years, spiny dogfish was the species caught in the greatest quantity (8.4 t or 1.4% of the total catch), and had the highest biomass estimate. The biomass estimate for giant stargazer was the highest in the series (Table 4, Figure 3). Although the large mode of adult females at cm is again apparent, the low numbers of females greater than 70 cm and males greater than 60 cm total length is consistent with the previous three surveys. The total biomass estimate for red gumard was higher than in 5 and the abundance in Tasman and Golden Bays has recovered to the levels seen in the first four surveys (Table 4). The biomass estimate of pre-recruit red gumard was almost twice that of5 and the highest since 0. The length frequency distribution for spiny dogfish shows very few fish under 50 cm. This is in contrast to all previous surveys on which spiny dogfish were measured where there is a strong mode 13

15 in the length frequency distributions at cm. It is not known if this IS a result of availability/catchability factors or indicates an actual absence of smaller fish. The biomass estimate for tarakihi declined from the very high level of 5 and is now similar to estimates from the 1990s. The mode at 15-3 cm is the strongest for this age class since the first survey in 199 (Figure 6m). It is difficult to track year classes through the research survey series in recent years, partly because of the intermittent nature of the series and partly because of the merging of modes as the fish grow. To determine if the + year class provides strong recruitment to the TAR 7 stock would require ageing of the commercial catch over the next -5 years. The strong mode at cm in the gemfish length frequency in 5 is no longer apparent and the gemfish catch was well below that of the previous two surveys. For John dory, the biomass estimate was down only slightly from 5 (Table 4). However, the current estimate is for fewer and larger fish and the strong modes of smaller fish (less than 35 cm) seen in 0 and 3 are again absent. There were few large ling, rig, or school shark caught compared to earlier surveys, but there were more smaller fish (Figures 6g, 6j, and 6k). The numbers of pre-recruit hake was similar to that in 5 but the number of pre-recruit hoki was about one-third those of 5 (Figure 7). There was an increase in the number of pre-recruits caught for blue cod, giant stargazer, ling, red gumard, tarakihi, rig, school shark, and silver warehou compared to 5. For rig, the numbers were the highest since 1995 and for school shark they were the highest for any survey. In contrast, few prerecruits were caught for John dory or jack mackerel (T declivis) compared to earlier surveys. 5. RECOMMENDATIONS The MFish medium term-research plan calls for another survey in this series in 9. The review of non-target species has shown the need for additional ageing studies for barracouta, blue warehou, hake, hoki, jack mackerel (both T declivis and T novaezelandiae), and silver warehou to determine if the sub-adult catch on these surveys is indicative of year-class strength. 6. ACKNOWLEDGMENTS This report is in partial fulfilment of the reporting requirements for MFish project INT60 1. I thank the skipper of RV Kaharoa, M. Baker, and his crew for their active cooperation and enthusiastic assistance during the trawl survey. Other scientific staff were Michael Manning, Colin Sutton, Rob Merrilees, Warrick Lyon, Christopher Dick, and Derrick Parkinson. Their hard work and dedication were much appreciated. Thanks also to the NIW A invertebrate group for identification of invertebrate specimens. Michael Beentjes provided very useful comments as referee. 7. REFERENCES Drummond, K.L.; Stevenson, M.L. (l995a). Inshore trawl survey of the west coast South Island and Tasman and Golden Bays, March-April 199 (KAH904). New Zealand Fisheries Data Report No p. Drummond, K.L.; Stevenson, M.L. (1995b). Inshore trawl survey of the west coast South Island and Tasman and Golden Bays, March-April 1994 (KAH9404). New Zealand Fisheries Data Report No p. 14

16 Drummond, K.L.; Stevenson, M.L. (1996). Inshore trawl survey of the west coast South Island and Tasman and Golden Bays, March-April 1995 (KAH9504). New Zealand Fisheries Data Report No p. Francis, R.LC.C. (1981). Stratified random trawl surveys of deep-water demersal stocks around New Zealand. Fisheries Research Division Occasional Publication No. 3.8 p. Francis, R.LC.C. (1984). An adaptive strategy for stratified random trawl surveys. New Zealand Journal of Marine and Freshwater Research 18: Francis, R.LC.C. (1989). A standard approach to biomass estimation from bottom trawl surveys. New Zealand Fisheries Assessment Research Document 89/3. 3 p. (Unpublished report held in NIW A library, Wellington.) Ministry of Fisheries (7). Report from the Fishery Assessment Plenary, May 7: stock assessments and yield estimates p. (Unpublished report held in NIW A library, Wellington. ) Stevenson, M.L. (1998). Inshore trawl survey of west coast South Island and Tasman and Golden Bays, March-April 1997 (KAH9701). NIWA Technical Report 1.70 p. Stevenson, M.L. (). Inshore trawl survey of west coast South Island and Tasman and Golden Bays, March-April 0 (KAH0004). NIWA Technical Report p. Stevenson, M.L. (4). Inshore trawl survey of the west coast South Island and Tasman and Golden Bays, March-April 3 (KAH0304). New Zealand Fisheries Assessment Report p. Stevenson, M.L.; Hanchet, S.M. (Comps.) (1999). Trawl survey design and data analysis procedures for inshore fisheries research. NIWA Technical Report 53.0 p. Stevenson, M.L.; Hanchet, S.M. (0). Review of the inshore trawl survey series of the west coast of the South Island and Tasman and Golden Bays, NIWA Technical Report p. Stevenson, M.L.; Hanchet, S.M. (7). Review of the data collected by the west coast South Island inshore trawl series to determine for which species relative abundance trends and size comparison information should be provided in each survey report. Final Research Report for Ministry of Fisheries Research Project INT60l, Objective p. (Unpublished report held in NIWA library, Wellington.) Vignaux, M. (1994). Documentation of Trawlsurvey Analysis Program. MAP Fisheries Greta Point Internal Report No p. (Unpublished report held in NIW A library, Wellington.) 15

17 Table 1: Stratum depth ranges, survey area, non-trawlable area, number of successful phase 1 and phase biomass stations, and station density. Non-trawlable Number of stations Station density Stratum Depth (m) Area (km ) area (km ) Phase 1 Phase (km per station) I I ~ Total (average) (371 ) 16

18 Table : Gear parameters for bimass stations by depth range (n, number of stations; s.d., standard deviation). Data for gear trials shown separately. n Mean s.d. Range All stations 69 Headline height (m) Doorspread (m) Distance (n. miles) Warp:depth ratio Tasman/Golden Bays 0-70 m 1 Headline height (m) Doorspread (m) Distance (n. miles) Warp:depth ratio West coast 0-m 57 Headline height (m) Doorspread (m) Distance (n. miles) Warp:depth ratio m 4 Headline height (m) Doorspread (m) Distance (n. miles) Warp:depth ratio m 4 Headline height (m) Doorspread (m) Distance (n. miles) Warp:depth ratio m 9 Headline height (m) Doorspread (m) Distance (n. miles) Warp:depth ratio

19 Table 3: Mean catch rates (kg.km- ) with standard deviations (in parentheses) by stratum for the 0 most abundant commercially important species in order of catch abundance. Species codes are given in Appendix 3. Sjecies code Stratum SPD BAR GSH RCO STA NOS TAR SCH HOK GUR (19) (135) (7) (63) (34) (30) (1) (36) (1) (9) (105) (37) (189) (18) (9) (6) (1) (19) (34) (153) (10) (45) (14) (5) (14) (1) (34) (11) (51) (41) (+) (5) (15) (33) (4) (1) (93) (79) (43) (55) (50) (75) (8) (14) (5) (1) (169) (158) (13) (5) (43) (31) () (4) (6) () (5) (33) (31) (48) (91) (71) (35) (74) (79) (58) (3) (65) (30) (04) (15) (80) (47) (64) (18) (153) (553) (1) (36) (40) (5) (18) (49) (18) (153) (8) (9) (36) (57) (488) (6) (14) (9) (7) (1337) (6) (8) (60) (49) (15) (131) (171) (15) (17) (17) (37) (313) (31) (9) (150) (10) (9) (9) (13) (8) (4) (11) (5) (11) (1) (19) (5) (53) (1) (17) (+) (61) (119) (75) (171) (50) (10) () (18) (47) (86) + < 0.5 kg.km- 18

20 Table 3-continued SEecies code Stratum FRO SPO HAK WAR RSK LEA JMN LIN JDO SWA (15) (44) (131) (19) (14) (38) (30) () (5) (5) () (9) (35) (80) (1) (16) (11) (8) (+) (+) (17) (5) () (31) (13) (7) (57) (1) (15) (9) (1) (95) (1) (5) (+) () (9) (13) () () (13) (+) (7) (73) (11) (30) (6) (1) (9) (17) (13) (3) () (17) (3) (5) (198) (38) (1) (+) (11) (1) (50) (11) (17) (6) (1) (54) (9) (3) (81) (15) (170) () (17) (1) (7) (3) (33) (1) (4) (+) (11 ) (4) (16) (16) (45) () (16) (9) (1) (1) (41) (97) (130) () (8) (1) + < 0.5 kg.km- 19

21 Table 4: Relative biomass estimates and c.v.s by trip from the entire survey area for ITQ species. Species Arrow squid Barracouta Blue warehou Dark ghost shark Elephantfish Frostfish Gernfish Giant stargazer Hake Hoki Jack mackerel Trachurus declivis T novaezelandiae John dory Leatherj acket Lemon sole Ling New Zealand sole Northern spiny dogfish Red cod Redgumard Rig Rough skate Sand flounder School shark Sea perch Silver warehou Smooth skate Spiny dogfish Tarakihi KAH904 Biomass cv% KAH9404 Biomass cv% KAH9504 Biomass cv% KAH9701 Biomass cv% KAH0004 Biomass cv% KAH0304 Biomass cv% III KAH0503 KAH0704 Biomass cv% Biomass cv%

22 Table 5: Recruited biomass estimates (t). Tasman and Total survey Recruited Golden Ba,Z:s West coast area Species length (cm) Biomass c.v.% Biomass c.v.% Biomass c.v.% Barracouta Blue warehou Giant stargazer Hoki John dory Ling Red cod Red gumard Rig Sand flounder School shark Silver warehou Tarakihi Table 6: Biomass estimates (t) by year class estimated from length frequency distributions. Year Length Species class range (cm) Biomass c.v.% Barracouta 0+ < Blue warehou 0+ < Hake 0+ < Hoki Jack mackerel (T. novaezelandiae) Red cod 0+ < Redgumard School shark 0+ < Silver warehou Tarakihi

23 Table 7: Estimated biomass (t) (and c.v.%) by stratum for the 0 most abundant commercially important species in order of catch abundance. Species codes are given in Appendix 3. SEecies code Stratum SPD BAR OSH RCO STA NOS TAR SCH HOK OUR (36) (38) (79) (55) (93) (55) (5) (94) () (65) (34) (88) (36) (89) (31) () (55) (69) (46) (87) (54) (79) (55) (74) (64) () (64) (4) (43) (18) () (96) (9) (81) () () (35) (57) (51) (46) (7) (59) (91) (41) () (46) (34) (51) (86) (54) (16) (3) (47) (34) () (60) () (85) (64) (15) () (95) (39) (37) (37) (58) (33) (35) 1 #### () (6) (4) (34) (1) (9) (39) (40) (67) () (63) (7) (5) (56) (49) (33) (51) () () (55) (59) () (68) (45) (6) (94) (79) (85) () (1) (6) (39) (35) (86) (11 ) (8) () (75) (68) (6) (0) (63) () (1) (76) (59) (31) (64) (33) (79) (37) (39) (40) (44) (55) () (43) (65) (64) (3) (55) (34) (78) (40) (1) (99) (46) (35)

24 Table 7-continued SEecies code Stratum FRO spa HAK WAR RSK LEA JMN LIN JDO SWA (67) (81) () (97) (76) () (9) (81 ) (94) () (64) (99) (74) (96) (85) () (58) () () () (67) (51) (46) (35) (7) (90) (6) () (98) (58) (8) () () () () (6) (57) (88) (87) () (78) (54) (49) (53) (51) (44) (67) (58) (3) (50) (66) (50) () (46) () (39) () (l00) () () (79) () () (89) (9) (47) () () () (93) (86) (78) (34) (59) (l00) (8) () (19) (67) (56) (81) (37) (6) (5) (49) (50) () (53) (76) (7) (87) (33) (70) () (35) (48) (77) (86) (37) (49) 3

25 Table 8: Number of biological and length frequency records. Length fre9uenc~ data Biological data+ Species Measurement No. of No. of No. of No. of No. of otoliths No. of code method samples fish samples fish or spmes tagged fish BAR BCO BRI 7 15 cm ELE EMA ESO 1 0 FRO GSH G GUR HAK HAP 4 6 HOK JAV 168 JDO 1 78 JMD 9 11 JMM 8 14 JMN KAH 1 3 LDO LEA LIN LSK 5 3 LSO MDO NOS NSD OPE 4 POS 1 RCO RSK SCH SCI B 1 SFL 7 59 SKI 10 9 SNA 6 16 SPD SPE SPO SSH 31 SSK STA SWA TAR THR TUR WAR YBF 1 1 Measurement methods: 1, fork length;, total length; 4, mantle length; 5, pelvic length; B, carapace length; G, total length excluding tail filament + Data include one or more of the following: fish length, fish weight, gonad stage, otoliths, spines 4

26 Table 9: Numbers of the four target species sampled at each reproductive stage (small fish of undetermined sex are not included). Males Females Gonad stage Gonad stage Total length (cm) Giant stargazer > Total Red cod > Total Red gurnard Total Tarakihi Total Gonad stages used were: 1, immature or resting;, maturing (oocytes visible in females, thickening gonad but no milt expressible in males); 3, mature (hyaline oocytes in females, milt expressible in males); 4, running ripe (eggs and milt free flowing) ; 5, spent (gonads flacid and bloodshot) 5